See also the related category hebrew.
Casiell is not popular as a baby boy name. It is listed outside of the top 1000.
Baby names that sound like Casiell include Cadwal (Welsh), Caeble, Caele, Caell, Cahal (Irish), Caheal, Caheel, Caheil, Cahil, Cahill, Cahyl, Caley (English and Scottish), Calie, Calli (English), Callie (English), Cally (English and Scottish), Cashel, Cassiell, Caswel, and Caswell (English).
† approx English pronunciation for Casiell: K as in "key (K.IY)" ; EY as in "ate (EY.T)" ; S as in "see (S.IY)" ; IY as in "eat (IY.T)" ; L as in "lay (L.EY)"