Analysis of information sources in references of the Wikipedia article "Maghull" in English language version.
The second el. of the name is obviously O.E. halh " haugh." This word here refers to the very gently sloping fields E. of the old mossland along the Alt. The first el. is not easy to explain. It appears to have had the form Magh- [ma3J in the earliest M.E. ; later [3] became [x] perhaps owing to assimilation with the h of the second el., and disappeared. Many names in -halh have a pers. n. as first el., and it is reasonable to suppose that also that of Maghull is one. But there is no (O.E. or O.N.) pers. n. that fits the name. O.E. mago " son," only used in poetry, might be thought of (cf. Childwall), but there are to my knowledge no other place-names in which the word is used. But O.E. Maga corresponding to O.H.Gr. Mago may well have existed. Another possibility is that the first el. of Maghull, like that of Mayfield, Suss. (Magefeud 1260, Maghfeud 1274, Maghefeld 1316, 1343; Roberts), is the Celtic *magos "plain" (Brit. *mag, whence Welsh ma "place," Ir. magh "plain, field," etc.). This derivation seems unexceptionable from the point of view of form and meaning. Brit, mag, i.e., [ma3], would not have lost its final consonant at the time when Lancashire was conquered by the Anglians ; cf . Douglas infra. Maghull occupies a plateau rising slightly over the low-lying land E. and W. This plateau is mostly level and would be aptly described as a plain. If the etymology suggested is correct, we must assume that the Brit, name of it was, or contained, the word mag "plain."