Origin and history of entrust

c. 1200, "reliance on the veracity, integrity, or other virtues or sound principles of someone or something; religious faith," probably from Old Norse traust "help, confidence, protection, support," from Proto-Germanic abstract noun *traustam (source also of Old Frisian trast, Dutch troost "comfort, consolation," Old High German trost "trust, fidelity," German Trost "comfort, consolation," Danish trøst, Gothic trausti "agreement, alliance").

This is reconstructed to be from Proto-Germanic *treuwaz, source of Old English treowian "to believe, trust," and treowe "faithful, trusty" (from PIE root *deru- "be firm, solid, steadfast;" compare trow (v.), true (adj.)).

It is attested from c. 1300 as "reliability, trustworthiness; trustiness, fidelity, faithfulness;" from late 14c. as "confident expectation" and "that on which one relies."

It is recorded from early 15c. in the legal sense of "confidence placed in a person who holds or enjoys the use of property entrusted to him by its legal owner;" and by mid-15c. as "condition of being legally entrusted," hence "that which is committed to one for safekeeping or use."

The meaning "businesses organized to reduce competition; an organization for the control of several corporations under one direction" by a set of majority shareholders in all of them, is a legal sense attested by 1877 which exploded as a U.S. political issue, hence trust-buster, recorded by 1903.

obsolete form of entrust (q.v.). Related: Intrusted; intrusting.

word-forming element meaning "in; into," from French and Old French en-, from Latin in- "in, into" (from PIE root *en "in"). Typically assimilated before -p-, -b-, -m-, -l-, and -r-. Latin in- became en- in French, Spanish, Portuguese, but remained in- in Italian.

Also used with native and imported elements to form verbs from nouns and adjectives, with a sense "put in or on" (encircle), also "cause to be, make into" (endear), and used as an intensive (enclose). Spelling variants in French that were brought over into Middle English account for parallels such as ensure/insure, and most en- words in English had at one time or another a variant in in-, and vice versa.