"knitted or woven covering for the foot, short stocking," early 14c., from Old English socc "slipper, light shoe," from Latin soccus "slipper, light low-heeled shoe," probably a variant of Greek sykchos, word for a kind of shoe, perhaps from Phrygian or another Asiatic language. The Latin word was borrowed generally in West Germanic (Middle Dutch socke, Dutch sok, Old High German soc, German Socke). To knock the socks off (someone) "beat thoroughly" is recorded from 1845, American English colloquial. Teen slang sock hop is c. 1950, from notion of dancing without shoes.
1700, "to beat, hit hard, pitch into," of uncertain origin. To sock it to (someone) is attested by 1877.
"to stash (money) away as savings," 1942, American English, from the notion of hiding one's money in a sock (see sock (n.1)).