means A large inland body of standing water, surrounded by land and usually fed and drained by rivers or streams.

from From Old French 'lac' and directly from Latin 'lacus' — a basin, pond, or reservoir. The same Latin root gives us 'lagoon' (via Italian 'laguna'), and it's a likely cousin of the Greek 'lakkos,' a pit or pond. There's also an Old English word 'lacu' meaning stream or watercourse, so two streams quietly fed into the modern word.