Hi
Nancy,
Several sites suggest that Maille is a Gaelic form of
Molly, however all of these sites are well-known for inventing meanings for made-up names or changing the meanings of real names. So they can't be trusted.
Maille could be a variation of
Maile (click hyperlink for details).
I also found this possible derivation of Maille:
Origin of the Surname O'Malley
The descendant of Malley; Mala, Gaelic, the brow of a hill; Maille, smooth, placid, gentle.
Source: An Etymological Dictionary of Family and Christian Names With an Essay on their Derivation and Import; Arthur, William, M.A.; New York, NY: Sheldon, Blake & CO., 1857.
I found that here:
http://www.searchforancestors.com/surnames/origin/o/omalley.php and as you can see they have given a reputable reference.
:-)