vulgar slang How are you? "They" refers to the testicles. Hey Ben, haven't seen you in a while. How they hanging?
How they hanging?
verb
See How’re they hanging?
How(’re) they hanging?
and How’s it hanging?
interrog. an inquiry calling for a report on (1) they, the state of a male’s testicles, (2) it the state of a male’s penis. You’re looking okay. How’re they hanging? Hey, dude! How’s it hanging?