1520s, "of or pertaining to a beginning," from French initial or directly from Latin initialis "initial, incipient, of the beginning," from initium "a beginning, a commencement; an entrance, a going in," noun use of neuter past participle of inire "to go into, enter upon, begin," from in- "into, in" (from PIE root *en "in") + ire "to go" (from PIE root *ei- "to go"). Related: Initially.
"accompanying, conjoined with, concurrent, going together," c. 1600, from French concomitant, from Late Latin concomitantem (nominative concomitans), present participle of concomitari "accompany, attend," from assimilated form of com "with, together" (see con-) + comitari "join as a companion," from comes (genitive comitis) "companion," "companion, attendant," the Roman term for a provincial governor, from com "with" (see com-) + stem of ire "to go" (from PIE root *ei- "to go"). Related: Concomitantly; concomitance (1530s).
mid-14c., "having to do with the past," from Old French preterit "past tense" (13c.) and directly from Latin praeteritum (as in tempus praeteritum "time past"), past participle of praeterire "to go by, go past," from praeter "beyond, over; more than" (see preter-) + itum, past participle of ire "to go" (from PIE root *ei- "to go").
Grammar sense is late 14c. The word also was a noun in Middle English meaning "past times" (late 14c.). Related: Preteritive. Preterite-present attested from 1813.
In some senses the English word is a back-formation from initiation. Related: Initiated; initiates; initiating; initiator.