Where does “clann” come from?

clann (Irish) comes from Middle Irish clann, from Old Irish cland, from Old Welsh plant, from Latin planta, from Proto-Italic plāntā, from Proto-Indo-European pléh₂-n̥t-eh₂, from Proto-Indo-European pleh₂- — flat.

clann (Irish): children, offspring; race, descendants, clan;...