c. 1300, "spearhead" (originally one shaped like a plowshare), from Anglo-French soket "spearhead, plowshare" (mid-13c.), diminutive of Old French soc "plowshare," from Vulgar Latin *soccus, perhaps from a Gaulish source, from Celtic *sukko- (source also of Welsh swch "plowshare," Middle Irish soc "plowshare"), properly "hog's snout," from PIE *su- "pig" (source also of Latin sus "swine;" see sow (n.) "female pig").
Meaning "hollow part or piece for receiving and holding something" first recorded early 15c.; anatomical sense is from c. 1600; domestic electrical sense first recorded 1885. Socket wrench is attested from 1837. The verb is 1530s, from the noun. Related: Socketed; socketing.