"indwelling, remaining within, inherent," 1530s, via French immanent (14c.) or directly from Late Latin immanens, present participle of immanere "to dwell in, remain in," from assimilated form of in- "into, in, on, upon" (from PIE root *en "in") + Latin manere "to dwell" (from PIE root *men- (3) "to remain"). In medieval philosophy contrasted with transitive; later with transcendent. Related: Immanently.
mid-15c., cohabitacioun, "action or state of living together," from Old French cohabitacion "cohabitation; sexual intercourse," or directly from Late Latin cohabitationem (nominative cohabitatio), noun of action from past participle stem of cohabitare "to dwell together," from co- "with, together" (see co-) + habitare "to live, inhabit, dwell," frequentative of habere "to have, to hold, possess" (from PIE root *ghabh- "to give or receive"). Specifically "state of living together as husband and wife without benefit of marriage," implying sexual intercourse, from 1540s.
The most famous was that of Delphi. Madison and other U.S. Founders devoted close study to it. Shaftesbury has amphictyonian (1711).