This hortatory expression is often used to signify “relax!”, “keep calm”, “take it easy”, “enjoy life”, etc. Many Internet sites offer definitions, but none that I can find actually explain the term, or give any clue as to its origins.
I have at the back of my mind the idea that the phrase refers to the cremaster muscles, from which are suspended the testicles of a fully equipped human male. Normally, these muscles are relaxed, and the testicles hang loose: during emotional stress, or sexual arousal, they contract, drawing the testicles upward (this is the reason for “sore balls” in males who experience prolonged, unresolved sexual excitation).
Can anyone throw any light on the origin and meaning of the term “hang loose”?