"extremely small," mid-15c., from earlier noun use in sense of "quantity, amount" (such as a littel wei "a little thing or amount," c.1300), from Old English wæge "weight" (see weigh). Adjectival use wee bit apparently developed as parallel to such forms as a bit thing "a little thing." Wee hours is attested by 1891, from Scottish phrase wee sma' hours (1819). Wee folk "faeries" is recorded from 1819. Weeny "tiny, small" is from 1790.