Relay
late Middle English (referring to the provision of fresh hounds on the track of a deer): from Old French relai (noun), relayer (verb), based on Latin laxare ‘slacken’.
wiktionary
From Middle French relai(“reserve pack of hounds”), from relaier(“to exchange tired animals for fresh”); literally, "to leave behind", from Old French relaier(“to leave behind”), from re- + laier(“to leave”), of uncertain origin.
re- + lay
etymonline
relay (n.)
late 14c., in hunting, relai, "hounds placed along a line of chase" (to replace those that tire), from Old French relais "reserve pack of hounds or other animals; rest, stop, remission, delay" (13c.), from relaier "to exchange tired animals for fresh," literally "leave behind," from re- "back" (see re-) + laier "leave, let."
This is perhaps a variant of Old French laissier, (compare Old French relaisser "release"), from Latin laxare "slacken, undo" (see lax (adj.)). But Watkins has it from Frankish *laibjan, from a Proto-Germanic causative form of PIE root *leip- "to stick, adhere."
The etymological sense is "to leave (dogs) behind (in order to take fresh ones)." Of horses, 1650s. As "a squad of men to take a spell or turn of work at stated intervals," by 1808. As a type of foot-race, it is attested from 1898. The electromagnetic instrument is attested by name from 1860, originally in telegraphy.
relay (v.)
c. 1400, relaien, "to set a pack of (fresh) hounds after a quarry;" also "change horses, take a fresh horse," from Old French relaiier, from relai (see relay (n.)). The word seems to have faded out by 19c. but was re-formed in electromagnetics from the noun, in a transitive sense of "pass on or retransmit," originally of telephone signals (1878), later in a transferred sense of "pass on information" (by 1956). Related: Relayed; relaying.
