"act of forsaking or abandoning," 1590s, from Middle French désertion (early 15c.), from Late Latin desertionem (nominative desertio) "a forsaking, abandoning," noun of action from past-participle stem of Latin deserere "to abandon, to leave, forsake, give up, leave in the lurch," from de "undo" (see de-) + serere "join together, put in a row" (from PIE root *ser- (2) "to line up"). In law, "willful withdrawal of one of the married parties from the other without cause or justification." Earlier in astrology, "forsaking or withdrawal of a favorable influence" (mid-15c.).