continual (adj.)

early 14c., continuell, "proceeding without interruption or cessation; often repeated, very frequent," from Old French continuel (12c.) and directly from Latin continuus "joining, connecting with something; following one after another," from continere (intransitive) "to be uninterrupted," literally "to hang together" (see contain).

That which is continual is that which is either always going on or recurs at short intervals and never comes to an end; that which is continuous is that in which there is no break between the beginning and the end. Related: Continually "always, incessantly, constantly" (c. 1300, contynuelliche).