1. When you are born, you are wearing nothing, so that can be our first idiom: your 'birthday suit' means 'naked'. Example: 'I couldn't answer the door as I was in my birthday suit.' And while we're on the subject of suits, many people such as managers and investment bankers wear them to the office. Example: He looked smart in his brand-new suit. With such a suit, one usually wears a white shirt, so a 'white-collar worker' is based in an office. Those who are involved in a trade (mechanics, electricians etc) are 'blue-collar workers'. If you gamble a lot, you might end up 'losing your shirt'. Example: 'That investment was a disaster. I've lost my shirt on it.' A very generous person is one 'who would give you his shirt off his back'. 'Keep your shirt on' is the same as the more trendy 'keep cool'. If you are in a bad mood and speak sharply to someone, they might tell you to stop being so 'shirty'. Shirt sleeves are a good place to hide things. Hence, 'Don't worry. I've got something up my sleeve' means that I have a good plan and might still be successful at something. If I 'cuff' you, I hit you around your ear. And if you do something 'off the cuff', you do it without preparation (usually a comment on something).
2. Belts were used to beat people, so to be given 'a belting' means to be hit. 'Belt up' can be an instruction to put on your safety belt or to shut up ('put a sock in it' and 'button it' mean the same thing - in a rude way). In boxing low punches are not allowed, so to hit someone 'below the belt' is to treat them unfairly. In martial arts, the best fighters are 'black belts', and areas around the city are called belts. Example: 'They are keeping that area as a greenbelt.' Belts hold up trousers (or pants) and the boss is the one who 'wears the trousers'.
3. Now let's go up to the head. If you want to attract the attention or love of someone, you 'set your cap at them'. If you need to think deeply about something, you 'put your thinking cap on'. A cap can also be a limit. Example: 'The government has set a cap on new spending. If you represent your country at sports, you are 'capped' or you 'win a cap'. To ask for a favour from someone, you go 'cap in hand'. If you ask if someone's criticism is aimed at you, they may reply: 'If the cap fits, wear it.'
4. If you keep something 'under your hat', you keep it a secret. If you are proved wrong, you may have to 'eat your hat'. If someone is impressed by your work, they may 'take their hat off' to you. A person may wear more than one hat. A teacher might also be a writer and a parent, so you might ask which hat they are wearing when they speak on an issue. 'To throw your hat into the ring' means that you want to be considered a candidate for something such as an election. Let's take a look at the veil. You might want to 'draw a veil' over something embarrassing you did, and quite a few things that go on in the world are 'kept veiled in secrecy'.
5. Let's move to the feet. Some of these idioms will really 'knock your socks off'. If someone in your class isn't doing very well, you might tell them to 'pull their socks up'. And if they really 'work their socks off', they might pass. If not, they might be 'booted out' of school. After you've told them that, they should be 'shaking in their boots'. However, if they do very well and you are the one who is in trouble, 'the boot will be on the other foot'. They may even seek revenge and 'put the boot in' when you can't defend yourself. People may not sympathise with you at that time and say: 'Well, he got too big for his boots. This will teach him a lesson.' Still a person can always 'pull himself up by his bootstraps' and succeed. There are also plenty of idioms that include the word 'shoe'. Asking for advice, you might say: 'What would you do if you were in my shoes?' It is indeed a good thing to 'put yourself in someone else's shoes' and try to understand how they feel. When you take over a job from someone, people may wonder if you will ever be able 'to fill their shoes'.
6. If you are 'hand in glove' with someone, you are working very closely with them, usually in a negative way. If you 'take your gloves off' (this is another idiom from boxing), you are determined to play rough. Ancient knights wore metal hand covers called gauntlets, and to throw one down at someone's feet, was to challenge them to battle. Therefore, to 'throw down the gauntlet' is to challenge someone (to do something). 'To run the gauntlet' is to take a big risk.
