1) Short for ‘privy room’, that is a room where privacy is possible, a toilet or lavatory.
1419-20 remove thayre pryves that standys upon the kynges dyke, York
1538 an entry into a privy or jaques, Knaresborough
1654 paid for 3 times dressing the previe, Stockeld. Used attributively: 1528 In his owne chamber ... A prevey stole, York.