mave been very early as Moore has noted the names from 1511 and before! - entry reads:
COWELL and COWLE, contracted from Mac Cathmaoil (corrupted into Mac Cawell), 'Cathmaol's son.'

The personal name CATHMAOL has been explained as meaning 'battle heap.'

'Conor MAC CAWELL, chief of Kinel Ferady,' A.D. 1252.*
They were the ancient chiefs of Kinel Ferady, and were famous in Ireland for their learning, and the numerous dignitaries they supplied to the Church.

COWELL and COWLE are purely Manx names.

McGILCOWLE, McCOWLE, MCCOWELL, COWLE [1511], COWELL [1690] COWEL [1700], COWILL [1711], COWL [1728], COWEL [1737], COWIL [1777].

Bride, Andreas (vc), Marown, German, Lezayre, Patrick, Malew, Santon (c), elsewhere (u).