Online Etymology Dictionary

press (n.): "crowd, multitude," early 13c., from O.Fr. presse (11c.), from L. pressare (see press (v.1)). Sense of "to urge, compel, force" (now mostly in adj. pressing, 1705) is recorded from late 14c. Basketball defense so called from 1961. Meaning "machine for squeezing" (e.g. winepress) is recorded from mid-14c., from M.Fr. presse. Specific sense "machine for printing" is from 1530s; extended to publishing houses by 1570s and to publishing generally (in phrases like freedom of the press) c.1680. This gradually shifted c.1800-1820 to "periodical publishing, journalism." Meaning "journalists collectively" is attested from 1926. Press agent is from 1883; press conference is attested from 1937, though the thing itself dates to at least World War I. Press secretary is recorded from 1959.
press (v.1): "push against," c.1300, from O.Fr. preser (13c.), from L. pressare "to press," frequentative of pressus, p.p. of premere "to press, hold fast, cover, crowd, compress," from PIE *prem-/*pres- "to strike." Weight-lifting sense is attested from 1908.
press (v.2): "force into service," 1578, alteration (by association with press (v.1)) of prest (c.1360) "engage by loan, pay in advance," especially money paid to a soldier or sailor on enlisting, from L. præstare "to provide," from præ- "before" + stare "to stand," from PIE base *sta- "to stand" (see stet). Related to præsto (adv.) "ready, available."