mistrust (n.)

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.

prefix of Germanic origin affixed to nouns and verbs and meaning "bad, wrong," from Old English mis-, from Proto-Germanic *missa- "divergent, astray" (source also of Old Frisian and Old Saxon mis-, Middle Dutch misse-, Old High German missa-, German miß-, Old Norse mis-, Gothic missa-), perhaps literally "in a changed manner," and with a root sense of "difference, change" (compare Gothic misso "mutually"), and thus possibly from PIE *mit-to-, from root *mei- (1) "to change."

Productive as word-forming element in Old English (as in mislæran "to give bad advice, teach amiss"). In 14c.-16c. in a few verbs its sense began to be felt as "unfavorably," and it came to be used as an intensive prefix with words already expressing negative feeling (as in misdoubt). Practically a separate word in Old and early Middle English (and often written as such). Old English also had an adjective (mislic "diverse, unlike, various") and an adverb (mislice "in various directions, wrongly, astray") derived from it, corresponding to German misslich (adj.). It has become confused with mis- (2).