Train
late Middle English: from Old French train (masculine), traine (feminine), from trahiner (verb), from Latin trahere ‘pull, draw’. Early noun senses were ‘trailing part of a robe’ and ‘retinue’; the latter gave rise to ‘line of travelling people or vehicles’, later ‘a connected series of things’. The early verb sense ‘cause a plant to grow in a desired shape’ was the basis of the sense ‘instruct’.
wiktionary
From Middle English trayne(“train”), from Old French train(“a delay, a drawing out”), from traïner(“to pull out, to draw”), from Vulgar Latin *traginō, from *tragō, from Latin trahō(“to pull, to draw”), ultimately from Proto-Indo-European *tregʰ-(“to pull, draw, drag”). The verb was derived from the noun in Middle English.
From Middle English trayne(“treachery”), from Anglo-Norman traine, Middle French traïne, from traïr(“to betray”).
etymonline
train (n.)
early 14c., "a drawing out, delay;" late 14c., "trailing part of a skirt, gown, or cloak;" also "retinue, procession," from Old French train "tracks, path, trail (of a robe or gown); act of dragging," from trainer "to pull, drag, draw," from Vulgar Latin *traginare, extended from *tragere "to pull," back-formation from tractus, past participle of Latin trahere "to pull, draw" (see tract (n.1)).,
General sense of "series, progression, succession, continuous course" is from late 15c.; train of thought is attested from 1650s. The railroad sense "locomotive and the cars coupled to it" is recorded from 1820 (publication year, dated 1816), from the notion of a "trailing succession" of wagons or carriages pulled by a mechanical engine.
train (v.)
"to discipline, teach, bring to a desired state by means of instruction," 1540s, probably from earlier sense of "draw out and manipulate in order to bring to a desired form" (late 14c.), specifically of the growth of branches, vines, etc. from mid-15c.; from train (n.). Sense of "point or aim" (a firearm, etc.) is from 1841. Sense of "fit oneself for a performance by a regimen or exercise" is from 1832. The meaning "to travel by railway" is recorded from 1856. Related: Trained; training.
