Saturday \Sat"ur*day\ (?; 48), n. [OE. Saterday, AS. S[ae]terd[ae]g, S[ae]ternd[ae]g, S[ae]ternesd[ae]g, literally, Saturn's day, fr. L. Saturnus Saturn + AS. d[ae]g day; cf. L. dies Saturni.]

The seventh or last day of the week; the day following Friday and preceding Sunday.

Source: Webster's Revised Unabridged Dictionary (1913)