Is it ensure, insure, or assure?
"messenger," 1660s, from French envoyé "messenger," literally "one sent" (12c.), noun use of past participle of envoyer "send," from Vulgar Latin *inviare "send on one's way," from Latin in "on" (see in- (2)) + via "road" (see via (adv.)). The same French word was borrowed in Middle English to mean "a stanza of a poem sending it off to find readers" (late 14c.).