annexation (n.)

1610s, "that which is added;" 1620s, "union" (now obsolete); 1630s, "action of adding to the end or adding a smaller to a greater," from Medieval Latin annexiationem (nominative annexatio) "action of annexing," noun of action from past participle stem of annexare "to bind to," from ad "to" (see ad-) + nectere "to tie, bind" (from PIE root *ned- "to bind, tie"). The Middle English noun form was annexion "union; joining; territory acquired" (mid-15c.).