as·sail / əˈsāl/ • v. [tr.] make a concerted or violent attack on: the Scots army assailed Edward's army from the rear. ∎  (usu. be assailed) (of an unpleasant feeling or physical sensation) come upon (someone) suddenly and strongly: she was assailed by doubts and regrets. ∎  criticize (someone) strongly.DERIVATIVES: as·sail·a·ble adj.

assail XIII. — OF. asalir (mod. assaillir) :- popL. assalīre f. AS- + salīre leap.
Hence assailant XVI, after F. assaillant.