Английский Этимологический словарь - press (2)

- "force into service," 1578, alteration (by association with press (1)) of prest (c.1360) "engage by loan, pay in advance," especially money paid to a soldier or sailor on enlisting, from L. prжstare "to provide," from prж- "before" + stare "stand." Related to prжsto (adv.) "ready, available."