late 14c., "represent in visual arts; put into words," from Old French espresser, expresser "press, squeeze out; speak one's mind" (Modern French exprimer), Medieval Latin expressare, frequentative of Latin exprimere "represent, describe, portray, imitate, translate," literally "to press out" (source also of Italian espresso); the sense evolution here perhaps is via an intermediary sense such as "clay, etc., that under pressure takes the form of an image," from ex "out" (see ex-) + pressare "to press, push," from Latin premere "to press, hold fast, cover, crowd, compress" (from PIE root *per- (4) "to strike"). Related: Expressed; expresses; expressing; expressible.
late 14c., "stated explicitly, not implied, clearly made known" from Old French espres, expres (13c.), from Latin expressus "clearly presented, distinct, articulated precisely," past participle of exprimere (see express (v.1)). Also late 14c. as an adverb, "specially, on purpose;" it also doubled as an adverb in Old French. An express train (1841) originally was one that ran to a certain station.
1610s, "special messenger," from express (adj.). Sense of "business or system for sending money or parcels" is by 1794.