- alienation (n.)
- late 14c., "transfer of ownership, action of estranging," from Old French alienacion and directly from Latin alienationem (nominative alienatio) "a transfer, surrender, separation," noun of action from past participle stem of alienare "to make another's, part with; estrange, set at variance," from alienus "of or belonging to another person or place," from alius "another, other, different" (see alias (adv.)).
Middle English alienation also meant "deprivation of mental faculties, insanity" (early 15c.), from Latin alienare in a secondary sense "deprive of reason, drive mad;" hence alienist. Phrase alienation of affection as a U.S. legal term in divorce cases for "falling in love with someone else" dates to 1861.