Etymology 1 
whang (third-person singular simple present whangs, present participle whanging, simple past and past participle whanged)
- (chiefly of an object) To make a noise such as something moving quickly through the air.
- 1922, E. E. Cummings, The Enormous room:
- The holder of the torch grunted, and (after pausing a second at B.'s bed to inspect a picture of perfect innocence) banged out through the door which whanged to behind him...
- (informal, transitive) To throw with a rapid slamming motion.
- 1993, Ralph Moody, Edward Shenton (illustrator), The Fields of Home, page 31:
- I don't know how long it might have gone on if Grandfather hadn't lost his temper. He swung the bridle up over his head and whanged it down across the buckskin's rump.
- (US, slang) To whack or beat.
- I ought to have whanged him one in the eye.
Etymology 2 
Debuccalized (/θw/ > /hw/) from Scots thwang, cognate to thong.
Alternative forms 
whang (plural whangs)
- (UK, US, dialect, informal, dated) A leather thong.
- (slang) A penis.