Mac An Chléirigh
Mac an CHLÉIRIGH—VII—M'Anclery, M'Ecleary, M'Eclery, MacClery, MacCleary, Clery, Cleary, Clarke, [Clarkson, Clarson]; 'son of the clerk' (Irish 'cléireach'); a common Cavan surname, probably a variant of Ó Cléirigh, which see. It is now nearly always translated Clarke. Clarkson is the exact English equivalent.
Alphabetical Index to Irish Surnames