The particular commercial senses of "make safe against loss by payment of premiums; undertake to ensure against loss, etc." are from mid-17c. (replacing assure in that meaning). Related: Insured; insuring.
Commercial sense of "security against loss or death in exchange for payment" is from 1650s. Assurance was the older word for this specific sense (late 16c.). Compare insure.
"give a small present of money to," c. 1600, originally "to give, hand, pass," thieves' cant, perhaps from tip (v.3) "to tap." The meaning "give a gratuity to" is first attested 1706. The noun in this sense is from 1755; the noun meaning "piece of confidential information" is from 1845; and the verb in the sense "give private information to" is from 1883.
The popularity of the tale of the word's supposed origin as an acronym in mid-18th century English taverns seems to be no older than Frederick W. Hackwood's 1909 book "Inns, Ales and Drinking Customs of Old England," where it was said to stand for To insure promptitude (in the form to insure promptness the anecdote is told from 1946). A reviewer of the book in The Athenaeum of Oct. 2, 1909, wrote, "We deprecate the careless repetition of popular etymologies such as the notion that "tip" originated from an abbreviated inscription on a box placed on the sideboard in old coaching-inns, the full meaning of which was "To Insure Promptitude." Also see here.
late 14c., preserven, "keep safe or free from harm," also "act so as to insure that something does not occur," from Anglo-French preservare, Old French preserver, Medieval Latin preservare "keep, preserve," all from Late Latin praeservare "guard beforehand," from Latin prae "before" (see pre-) + servare "to keep safe" (from PIE root *ser- (1) "to protect").
From early 15c. as "maintain, keep in a certain quality, state or condition." Of fruit, etc., "prevent from spoiling by use of preservative substances," 1570s; of organic bodies, "keep in existence or alive," from 1610s. Related: Preserved; preserver; preserving.
"design stamped on wax," especially an impressed figure attached to a document as evidence of authenticity, c. 1200, sel, sele, from Old French seel, seal "seal on a letter" (Modern French sceau), from Vulgar Latin *sigellum (source of Italian suggello, Spanish sello; also Old Frisian and Middle High German sigel, German Siegel), from Latin sigillum "small picture, engraved figure, seal," diminutive of signum "identifying mark, sign" (see sign (n.)).
An earlier borrowing directly from Latin is represented by Old English insigel. The use for "engraved device of some hard material used for imprinting a seal" (technically a matrix) is by c. 1300. Extended senses are via the notion of a seal used to mark and close a document to insure its secrecy (c. 1300). The meaning "an identifying mark" is from mid-14c.; especially one confirming goods and measures as conforming to standard. The technical sense of "what prevents the escape of a gas or liquid" is by 1853.
