1350-1400; (v.) Middle English < Anglo-French,Old Frenchannexer < Medieval Latinannexāre, derivative of Latinannexus tied to, past participle of annectere (see annectent); (noun) < Frenchannexe or noun use of v.
late 14c., "to connect with," from Old French annexer "to join" (13c.), from Medieval Latin annexare, frequentative of Latin annecetere "to bind to," from ad- "to" (see ad-) + nectere "to tie, bind" (see nexus). Almost always meaning "to join in a subordinate capacity." Of nations or territories, c.1400. Related: Annexed; annexing.
n.
1540s, "an adjunct, accessory," from French annexe, from annexer (see annex (v.)). Meaning "supplementary building" is from 1861.