Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
MULL
As described in historical dictionaries
Patronymica Britannica (1860)
MULL. A topographical expression, as the midl of Cantire. In other cases it may mean mulne, 0. E. for mill. In Lancashire it is an abbreviated form of Molineux. " Our clergyman prayed at churcli for JIary Mull some time ere he found out that she Avas a \Iolineux. He may well be said to have " made a mvll of it !" From a Lancashire correspondent.