mid-15c., "lacking form; not in accordance with the rules of formal logic," from in- (1) "not, opposite of" + formal (adj.). Meaning "irregular, unofficial, not according to rule or custom" is from c. 1600. Sense of "done without ceremony" is from 1828. Related: Informally.

1560s, "a law or decree," from Latin sanctionem (nominative sanctio) "act of decreeing or ordaining," also "a decree, an ordinance, a law," noun of action from past-participle stem of sancire "to decree, confirm, ratify, make sacred" (see saint (n.)).

Originally especially of ecclesiastical decrees. The extended sense of "express authoritative permission" is by 1720, hence the looser sense of "the conferring of authority upon (an opinion, practice or sentiment); confirmation of support derived from public approval" (1738). Moral sanction, in Bentham's philosophy, is "the knowledge of how one's neighbors will take a given act, as a motive for doing or not doing it" [Century Dictionary].

As "a penalty enacted according to a provision in a law to enforce obedience to it" from 1630s; in later 17c. also "a provision of a law which enforces obedience through rewards or penalties." Hence the modern sense of "economic or quasi-military action by a state against another," usually to enforce terms of a law or treaty that has been violated (1919).

1778, "confirm by sanction, make valid or binding;" by 1797 as "to permit authoritatively," also in a general sense, "give countenance or support to, approve;" from sanction (n.). Seemingly contradictory meaning "impose a penalty on" is from 1956 but is rooted in an old legalistic sense of the noun. Related: Sanctioned; sanctioning.

1590s, from informal + -ity.

1906, American English, informal shortening of tarpaulin.

by 1987, informal. Related: Scooched; scooching.

in international diplomacy, by 1900, plural of sanction (n.) in the sense of "part or clause of a law which spells out the penalty for breaking it" (1650s).

1731, "clever, sharp, smart," shortening of acute; informal sense of "pretty" is by 1834, American English colloquial and student slang. Related: Cutely; cuteness.

"superlatively sacred or inviolable," c. 1600, from Latin sacrosanctus "inviolable, protected by religious sanction, consecrated with religious ceremonies," from sacro, ablative of sacrum "religious sanction, religious rite" (from neuter singular of sacer "sacred") + sanctus, past participle of sancire "make sacred" (for both, see sacred). Earlier in partially Englished form sacro-seint (c. 1500).

also para-transit, "public transportation of a flexible, informal kind" (such as taxis, carpools, etc.), 1973, from para- (1) + transit.