sock

From Middle English socke, from Old English socc ("sock, light shoe, slipper"), a West Germanic borrowing of Latin soccus, a light shoe or slipper worn by comic actors. Latin took it from Ancient Greek súkkhos, itself likely from Phrygian or another Anatolian language, with a possible deeper link to an Avestan word for the sole of the foot.

It began as a name for a whole light shoe or slipper in Greek and Latin, but by the time it settled into English as 'socc,' it had narrowed to the soft inner covering worn under a shoe rather than the shoe itself.

It's a doublet of zocco, and kin to zoccolo, socle, and zocalo — all descendants of that same Latin soccus. Note that the punching sense of 'sock' (a hit with the hand) is unrelated, likely imitative and echoed in Portuguese soco.