a fusion of Old English hon "suspend" (transitive, class VII strong verb; past tense heng, past participle hangen), and Old English hangian (weak, intransitive, past tense hangode) "be suspended;" also probably influenced by Old Norse hengja "suspend," and hanga "be suspended." All from Proto-Germanic *khang- (cf. Old Frisian hangia, Dutch hangen, German hängen), from PIE *kank- "to hang" (cf. Gothic hahan, Hittite gang- "to hang," Sanskrit sankate "wavers," Latin cunctari "to delay;" see also second element in Stonehenge). As a method of execution, in late Old English (but originally specifically of crucifixion).
Hung emerged as past participle 16c. in northern England dialect, and hanged endured only in legal language (which tends to be conservative) and metaphors extended from it (I'll be hanged). Teen slang sense of "spend time" first recorded 1951; hang around "idle, loiter" is from 1830, and hang out (v.) is from 1811. Hang fire (1781) was originally used of guns that were slow in communicating the fire through the vent to the charge. To let it all hang out "be relaxed and uninhibited" is from 1967.