Your Internet Service Provider gave you a user name which is used to authenticate you with their servers. It usually is the first part of your email address (the part before @).
Mae eich Darparwr Gwasanaeth Rhyngrwyd (ISP) wedi rhoi enw defnyddiwr i chi er mwyn eich dilysu gyda' i gweinyddion. Fel arfer, rhan gyntaf eich cyfeiriad ebost (y rhan cyn y @) yw hwn.