In 1685 Sir William Petty's map spells it Monemoling (a pronunciation which has survived to the present day). By 1837 the spelling had changed to Monemolin according to Samuel Lewis's Topographical Dictionary of Ireland. In 1851 The Index of Irish Townlands records it as Monomolin. However, Monamolin is the standardised spelling today.
The various English versions of the name all come from the Irish, Muine Moling. Saint Moling (d. 696) was a seventh-century Irish saint. O'Donaill's Irish-English Dictionary translates muine as "brushwood" or "scrub". Therefore, the name means "the brushwood" or "scrub of Moling".