Probably few times you heard some funny or strange expressions related to body parts. :) Don't worry it was just few common idioms. :) You can use them in many daily situations, I hope that from today you will use them at every opportunity!!
Good luck :)
To get cold feet (idiom): To suddenly become too frightened to do something you had planned to do, especially something important like getting married.
EX. We're getting married next Saturday - that's if Tracy doesn't get cold feet! I'm worried she may be getting cold feet about our trip to Patagonia.
Get something off your chest (idiom): To tell someone about something that has been worrying you or making you feel guilty for a long time.
EX. I had spent two months worrying about the matter and I was glad to get it off my chest.
Be in over your head (idiom): To be involved in a difficult situation that you cannot get out of.
EX. Sean tried to pay his gambling debts, but he was in over his head.
Let your hair down (idiom): To allow yourself to behave much more freely than usual and enjoy yourself.
EX. Oh let your hair down for once!
Stick your neck out (idiom): To take a risk.
EX. I’m really sticking my neck out by investing my money in this idea.
To play it by ear (idiom): To decide how to deal with a situation as it develops rather than planning how you are going to react.
EX. I'm not sure how long I'll stay at the party. I'll just play it by ear.