Signal
late Middle English: from Old French, from medieval Latin signale, neuter of late Latin signalis, from Latin signum ‘mark, token’ (see sign). The verb dates from the early 19th century.
wiktionary
From Old French segnal, seignal or Medieval Latin signāle; noun use of the neuter of Late Latin signālis, from Latin signum; verb use from 1805, as a shortened from signalize (1650s).
etymonline
signal (n.)
late 14c., "visible sign, indication," from Old French signal, seignal "seal, imprint, sign, mark," from Medieval Latin signale "a signal," from Late Latin signalis (adj.) "used as a signal, pertaining to a sign," from Latin signum "identifying mark, sign" (see sign (n.)). Restricted sense "agreed-upon sign (to commence or desist, etc.) is from 1590s. Meaning "modulation of an electric current" is from 1855.
signal (adj.)
"remarkable, striking, notable" ("serving as a sign"), 1640s, from French signalé, past participle of signaler "to distinguish, signal" (see signal (n.)).
signal (v.)
1805, "to make signals to," from signal (n.). Related: Signaled; signaling. Earlier verb was signalize (1650s).
