licit adj.

late 14c., "formal authorization, official permission, permit, privilege," from Old French licence "freedom, liberty, power, possibility; permission," (12c.), from Latin licentia "freedom, liberty; unrestrained liberty, wantonness, presumption," from licentem (nominative licens), present participle of licere "to be allowed, be lawful," from PIE root *leik- "to offer, bargain, make a bid" (possibly source also of Lettish likstu "I come to terms").

Meaning "formal (usually written) permission from authority to do something" (marry, hunt, drive, etc.) is first attested early 15c. Meaning "excessive liberty, disregard of propriety" in English is from mid-15c. In Middle English spelled licence, licens, lisence, lissens, licance. There have been attempts to confine license to verbal use and licence to noun use (compare advise/advice, devise/device, and see note in OED); in the U.S., license tends to serve as both verb and noun.

Poetic licence "intentional deviation from recognized form or rule" is from 1733, earlier as lycence poetycall (1530). The licence-plate is from 1870 (of dogs and wagons before automobiles); licence-number is by 1903.

"that is, namely, to wit," late 14c., a Latin word used in English, "you may know, you may be sure, it is certain," used in sense "that is to say, namely," a contraction of scire licit "it is permitted to know," from scire "to know" (see science); for second element see licit. It was used as was Old English hit is to witanne, literally "it is to wit" (see wit (v.)). Often abbreviated sc. or scil.

Its function is to introduce : (a) a more intelligible or definite substitute, sometimes the English, for an expression already used ... (b) a word &c. that was omitted in the original as unnecessary, but is thought to require specifying for the present audience .... [Fowler]