sanction (n.)

early 12c. as an adjective, seinte, "holy, divinely inspired, worthy of worship," used before proper names (Sainte Marian Magdalene, etc.), from Old French saint, seinte "holy, pious, devout," from Latin sanctus "holy, consecrated," past participle of sancire "consecrate" (see sacred). It displaced or altered Old English sanct, which is directly from Latin sanctus.

From an adjective prefixed to the name of a canonized person, it came to be used in English by c. 1200 as a noun, "a specific canonized Christian," also "one of the elect, a member of the body of Christ, one consecrated or set apart to the service of God," also in an Old Testament sense "a pre-Christian prophet."

It is attested by late 13c. as "moral or virtuous person, one who is pure or upright in heart and life."

The adjectives also were used as nouns in Late Latin and Old French: "a saint; a holy relic." The Latin word also is the source of Spanish santo, santa, Italian san, etc., and also ultimately the source of the word in most Germanic languages (Old Frisian sankt, Dutch sint, German Sanct).

Perhaps you have imagined that this humility in the saints is a pious illusion at which God smiles. That is a most dangerous error. It is theoretically dangerous, because it makes you identify a virtue (i.e., a perfection) with an illusion (i.e., an imperfection), which must be nonsense. It is practically dangerous because it encourages a man to mistake his first insights into his own corruption for the first beginnings of a halo round his own silly head. No, depend upon it; when the saints say that they—even they—are vile, they are recording truth with scientific accuracy. [C.S. Lewis, "The Problem of Pain," 1940]

late 14c., "hallowed, consecrated, or made holy by association with divinity or divine things or by religious ceremony or sanction," past-participle adjective from a now-obsolete verb sacren "to make holy" (c. 1200), from Old French sacrer "consecrate, anoint, dedicate" (12c.) or directly from Latin sacrare "to make sacred, consecrate; hold sacred; immortalize; set apart, dedicate," from sacer (genitive sacri) "sacred, dedicated, holy, accursed." OED writes that, in sacred, "the original ppl. notion (as pronunciation indicates) disappeared from the use of the word, which is now nearly synonymous with L. sacer."

This is from Old Latin saceres, from PIE root *sak- "to sanctify." Buck groups it with Oscan sakrim, Umbrian sacra and calls it "a distinctive Italic group, without any clear outside connections." De Vaan has it from a PIE root *shnk- "to make sacred, sanctify," and finds cognates in Hittite šaklai "custom, rites," zankila "to fine, punish." Related: Sacredness. The Latin nasalized form is sancire "make sacred, confirm, ratify, ordain" (as in saint, sanction). An Old English word for "sacred" was godcund.

The meaning "of or pertaining to religion or divine things" (opposed to secular or profane) is by c. 1600. The transferred sense of "entitled to respect or reverence" is from 1550s. Sacred cow as an object of Hindu veneration is by 1793; its figurative sense of "one who or that which must not be criticized" is in use by 1910 in U.S. journalism, reflecting Western views of Hinduism. Sacred Heart "the heart of Jesus as an object of religious veneration" is by 1823, short for Sacred Heart of Jesus or Mary.

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).