kulub

root. *root (as a kind of plant)

One of the Primitive Adûnaic roots Tolkien used to illustrate the processes of Primitive Adûnaic word formation (SD/422-5). It also seems to be the root of words such as kulbu and kulub “root (as a kind of plant)” (SD/431), perhaps an deliberate pun by Tolkien.

kulub

collective noun. roots, edible vegetables that are roots not fruits

A collective-noun meaning “all edible root vegetables”, as opposed to kulbu used for an individual root (SD/431).