Where does “laicus” come from?

laicus (Late Latin) comes from Ancient Greek λαϊκός, from Ancient Greek λᾱός, from Proto-Hellenic lāwós, from Proto-Indo-European leh₂wos, from Proto-Indo-European leh₂- — to bark, howl; to be concealed.

laicus (Late Latin): of the people; lay, layman, laic