Quoting from "The Place-Names of the Isle of Man", J.J.Kneen (original 1925, republished 1970 by the Manx Gaelic Society):
Kirk Maughold
Jalloo
In place-names usually means "a spectre, Phantom, or ghost" (Irish dealbh). This place is one of the particles and probably there was some legend connected with it which gave rise to the name,