means A point of release or exit — whether a socket that supplies electrical power, a stream draining a lake, a store that sells goods, or any channel for letting something out.

from A plain English compound of 'out' + 'let,' built the same way as 'inlet.' Here 'let' carries its old sense of 'allow to pass' (as in 'let out'), so an outlet is literally a place where something is let out — water, energy, emotion, or merchandise. The word goes back to Middle English; the electrical sense is a much later borrowing, arriving with household wiring around the early 20th century, while the retail 'outlet store' sense is newer still.