English: occupational name for a scribe or secretary, originally a member of a minor religious order who undertook such duties. The word
clerc denoted a member of a religious order, from Old English
cler(e)c ‘priest’, reinforced by Old French
clerc. Both are from Late Latin
clericus, from Greek
klerikos, a derivative of
kleros ‘inheritance’, ‘legacy’, with reference to the priestly tribe of Levites (see
Levy) ‘whose inheritance was the Lord’. In medieval Christian Europe, clergy in minor orders were permitted to marry and so found families; thus the surname could become established. In the Middle Ages it was virtually only members of religious orders who learned to read and write, so that the term
clerk came to denote any literate man.
Dictionary of American Family Names, Oxford University Press, ISBN 0-19-508137-4
In other words, when your illiterate ancestors couldn't even read, mine were writing.