I collect these. Additions to this list are welcome. Also note that in some cases I do not know the origin of a particular expression. If you have knowledge or original listings for anything below, I would also like to hear from you. I hope you use this.
Talking through your hat
To talk about bull or to lie. c1885. [In an interview in The World entitled “How About White Shirts”, a reporter asked a New York streetcar conductor what he thought about efforts to get the conductors to wear white shirts like their counterparts in Chicago. “Dey're talkin 'tru deir hats” he was quoted as replying.]
Eat Your Hat
There's nothing like that, but that's where this expression comes from. If you tell someone you will eat your hat if they do something, make sure you do not wear your best hat – just if you are. [The expression goes back at least to the reign of Charles II of Great Britain and had something to do with the amorous proclivities of 'ol Charlie. They also named a goat after him that had his same love of life which included, in the goat's case, eating hats.]
Old bad stuff; out of fashion. [This seems to come from the fact that hat fashions are constantly changing. The fact of the matter is that hat fashions had not been changing very fast at all until the turn of the 19th Century. The expression therefore is about 100 years old.]
Mad Like Hatter
Absolutely demented, crazy. [Hatters did, indeed, go mad. They inhaled fumes from the mercury that was part of the process of making felt hats. Not recognizing the violent twitching and derangement as symptoms of a brain disorder, people made fun of affected hat-makers, often treating them as drunkards. In the US, the condition was called the “Danbury shakes.” (Danbury, Connecticut, was a hat-making center.) Mercury is no longer used in the felting process: hat-making – and hat-makers – are safe.]
Hat in hand
Demonstration of humility. For example, "I get a hat in my hand" means I get into a feeling or in a weakness. [I assume that the origins are from feudal times when serfs or any lower members of feudal society were required to take off their hats in the presence of the lord or monarch (remember the Dr. Seuss book “The 500 Hats of Bartholomew Cubbins”? ). A hat is your most prideful adornment.]
Pass the Hat
Literally go with a hubby member of an audience or group as a way to raise money. Also pray or ask for charity work. [The origin is self-evident as a man's hat turned upside down makes a fine container.]
Strange as Dick's Hat Band
Anything that's too tight. [The Dick in this case is Richard Cromwell, the son of England's 17th Century “dictator”, Oliver Cromwell. Richard succeeded his dad and wanted to be king but was quickly disposed. The hatband in the phrase refers to the crown he never got to wear.]
Three consecutive successes in game or other quest. For example, taking three warriors with three successful pitches with the trick in cricket play, three goals or points a player won in football or hockey games, etc. [From cricket, from the former practice of awarding a hat to a bowler who dismissed three batsmen with three successful balls.]
In the 19th century, men who dressed Derby hats especially Eastern business people and later crooks, gambler and detectives. [Derby hats, aka Bowlers or Cokes, were actually very hard as they were developed in 1850 for use by a game warden, horseback rider wanting protection.] Today there are "hard caps" construction workers [for obvious reasons].
In hat, or hat
Expression of unfaithfulness. [Origin unknown. Help us if you can]
Throw a hat in the ring
Get in a race or race, such as a political run for an office. [Viðskiptavinurskrifaðiokkurmeðeftirfarandi"Églasí"TheLanguageofAmericanPolitics"afWilliamFBuckleyJraðorðasambandið"kastahúfuíhringnum"kemurfrástarfi19aldarsaloonkeeperssetjaboxhringímiðjubarroomsvoaðviðskiptavinirsemvilduberjastviðhvertannaðmyndihafastaðtilaðgeraþaðánþessaðhefjadonnybrook
At one point declared Theodore Roosevelt that he was running an office with a speech that contains a line that went something like" my hat is in the ring and I removed the "The words" My hat in the ring "is stuck, probably because" I'm removed in the waist. "is a bit gross.]
Hats Off. . .
" Hats to US Winter Olympic Team "for example. Exclusion of Approval or Kudos. [Origins must be from the fact that taking one's hat off or tipping one's hat is a traditional demonstration of respect.]
A Feather in Your Cover  Special Achievement. [I assume that the origins on this expression hail from the days when, in fact, a feather for one's cap would be awarded for an accomplishment much like a medal is awarded today and pinned to one's uniform. A feather, or a pin, add a certain prestige or luster to one's apparel.]
Continue Your Hat
Warning Anyone Activating or Canceling being dirty. [When riding horseback or in an open-air early automobile, the exclamation “hold on to your hat” when the horse broke into a gallop or the car took-off was certainly literal.]
Bee In Your Bonnet
Indication of turmoil or an idea that you can not let go and have to express. [A real bee in one's bonnet certainly precipitates expression.]
Wearing Many Hats
This is of course a metaphor for having many different jobs or jobs. [Historically, hats have often been an integral, even necessary, part of a working uniform. A miner, welder, construction worker, undertaker, white-collar worker or banker before the 1960s, chef, farmer, etc. all wear, or winter, a particular hat. Wearing “many hats” or “many different hats” simply means that one has different duties or jobs.]
All hats and no cattle
All shows and no content. For example, in October 2003, Elder Robert Byrd declared that Bush's statement that it would like the United Nations as a partner to transform Iraq were "All Hat and No Cattle." [This Texas expression refers to men who dress the part of powerful cattlemen, but do not have the herds back home.]
To hang your hat (or not)
To commit something (or not) or accept your reputation for something (or not), such as an idea or a policy. For example, "I would not hang my hat on George Steinbrenner's decision to shoot his manager." [Origin unknown. Can anyone help with this one?]
At the drop of hat
Fixed. [Dropping a hat, can be a way in which a race can start (instead of a starting gun for example). Also, a hat is an apparel item that can easily become dislodged from its wearer. Anyone who wears hats regularly has experienced the quickness by which a hat can fly off your head.]
To order your hat or tip on the hat
Accept dignity, acceptance, gratitude or the like. Example: "The skin of the skin for American soldiers to reach Saddam Hussein." [This is simply verbalizing an example of hat etiquette. Men would (and some still do) tip their hat to convey the same message.]
My hat replaces me
This is an expression from Ecuador, a home of Panama hat. That means what is said; It is your choice to give up your hat than your life. [The Guayas River runs through Guayaquil, Ecuador's largest city on the Pacific coast. People from the city were known to hunt alligators for their hides in the river by swimming stark naked wearing Panama hats on their heads and long knives between their teeth. When the reptiles open their jaws and go for the swimmer, he dives leaving his hat floating on the surface for the alligator to chew on while he plunges the knife into the animal's vitals. From THE PANAMA HAT TRAIL by Tom Miller.]
I think this is a French expression for a bad person. [Ludwig Bemelmans' MADELINE series of children's books, set in France, includes one MADELINE AND THE BAD HAT. In this story Madeline, our heroine, refers to a little boy neighbor as a “bad hat”. She clearly means this as a metaphor for a bad person and because I do not know the expression in English, I assume this is a common French reference. If anyone out there knows more about this, please drop us an email.]
Hat with hat
Step by step. [Nevada Barr's book SEEKING ENLIGHTENMENT: Hat by Hat means just that. Has anyone heard this expression otherwise? If yes, please email us.]
Keep something under your hat
Keep your secret. [People kept important papers and small treasures under their hats. One's hat was often the first thing put on in the morning and the last thing taken off at night, so literally keeping things under one's hat was safe keeping. A famous practitioner of this was Abraham Lincoln. The very utilitarian cowboy hat was also commonly used for storage.]
Here's your hat, but what are you in a hurry?
When someone has taken plenty of your time and you want him to understand. [Origin unknown.]
Carry his office in his hat
Manage business on shoestring. [Important papers and the like were often transported in one's hat.]
Sets her hat
A young woman "puts her hood" on a young man she hopes to be interested in marrying her. [Long ago, maidens wore caps indoors because homes were poorly heated. A girl set her most becoming hat on her head when an eligible fellow came to call.]
To put on the "thought cap" is a little thoughtful thought.
Black Hat. . .
Black hate methods, black hats, etc. Refer to unhappy actions or ideas. [Black hats in Western lore and literature were the bad guys.]
White Hat. . .
Although I do not see or hear this expression as much as "Black Hat", it's simply the opposite of the above. [Good guys wear / wear white hats.]
Source by Fred Belinsky