advowson (n.)

"a calling in of legal assistance," 1520s, from Latin advocationem (nominative advocatio) "a calling or summoning of legal assistance," in Medieval Latin "duty of defense or protection," noun of action from past-participle stem of advocare "to call, summon, invite; call to aid," from ad "to" (see ad-) + vocare "to call," which is related to vox (genitive vocis) "voice" (from PIE root *wekw- "to speak").