Lemon, Lemmon, Leeman
Lemon, Lemmon, Leeman, Lemondson—These four names are anglicised forms of M'Clymont (Mac Laomuinn). Buchanan says the Clan Lamond is descended from Lamond O'Neill, son of one of the O'Neills, Princes of Ulster. The dexter hand on the clan crest would lead to a confirmation of Buchanan's statement.
Alphabetical Index of Anglicised Surnames in Ireland
See also Woulfe’s Irish Names and Surnames
… and O'Hart's Irish Pedigrees