1797, "hiding place," from French Canadian trappers' slang, "hiding place for stores and provisions" (1660s), a back-formation from French cacher "to hide, conceal" (13c., Old French cachier), from Vulgar Latin *coacticare "store up, collect, compress," frequentative of Latin coactare "constrain," from coactus, past participle of cogere "to collect," literally "to drive together," from com- "together" (see co-) + agere "to set in motion, drive; to do, perform" (from PIE root *ag- "to drive, draw out or forth, move"). The sense was extended by 1830s to "anything stored in a hiding place."

"to act together," c. 1600, from co- + act (v.). Related: Co-action; co-active; co-actor.

also co-adaptation, "mutual or reciprocal adaptation," 1803, from co- + adaptation.

also co-adjacent, "mutually adjacent," 1842, from co- + adjacent. Related: Coadjacence.

1540s, "grow together, unite by growing into one body," from Latin coalescere "unite, grow together, become one in growth," from assimilated form of com- "together" (see co-) + alescere "be nourished," hence, "increase, grow up," inchoative of alere "to suckle, nourish," from PIE root *al- (2) "to grow, nourish." Related: Coalesced; coalescing; coalescence; coalescent.

"mutual or reciprocal articulation," 1610s, from co- + articulation.

also coauthor, "one who writes (a book, journal article, etc.) along with another," 1850, from co- + author (n.). From 1948 as a verb. Related: Co-authored; co-authoring.

also co-axial, "having a common axis," 1850 as a term in mathematics; the coaxial cable, one containing several coaxial lines, is attested by that name from 1934. See co- + axial. Earlier coaxal (1847). Related: Coaxially; coaxiation.

"one who is mutually at war" (as distinguished from an ally), 1813, a word from the Napoleonic wars, from co- + belligerent. As an adjective, "carrying on war in conjunction with another power," from 1828.

also codefendant, "one who is a defendant along with another," 1640s, from co- + defendant.