Proto-North Caucasian: *burVźV
Meaning: a k. of foliage tree
Notes: The root is obviously borrowed from an Iranian source (cf. Shugn. bǝruǯ, Osset. bärz / bärzä 'birch-tree' etc.); but since the reflexes correspond to each other well phonetically, are present in distant EC subgroups and have substantially modified the original semantics, the borrowing should be probably dated by a very early (common EC) period.
