Etymology of "laity"
The word laity (the body of religious worshipers, as distinguished from the clergy), comes from the French laite from the late Latin laicus, which is a transliteration of the Greek laikos (of the people; λαϊκός) from laos (people; λαός).
From the same root:
a) laos: people [λαός]
b) laikos: of the people, folk, vulgar [λαϊκός]
More: http://ewonago.blogspot.com/ [English Words of no Apparent Greek Origin]