Clan
late Middle English: from Scottish Gaelic clann ‘offspring, family’, from Old Irish cland, from Latin planta ‘sprout’.
wiktionary
Borrowed from Irish clann(“offspring, children of the family”) and Scottish Gaelic clann, both from Old Irish cland, borrowed from Old Welsh plant, itself borrowed from Latin planta(“shoot, offspring”). Doublet of plant.
etymonline
clan (n.)
"a family, a tribe," especially, among the Highlanders of Scotland, a form of social organization consisting of a tribe holding land in common under leadership of a chieftain, early 15c., from Gaelic clann "family, stock, offspring," akin to Old Irish cland "offspring, tribe," both from Latin planta "offshoot" (see plant (n.)).
The Goidelic branch of Celtic (including Gaelic) had no initial p-, so it substituted k- or c- for Latin p-. The same Latin word in (non-Goidelic) Middle Welsh became plant "children."
