Gloss “kulusta” by Eldamo Import

I have wonderings about this one.

CULU / KULU / CULO is stated as appearing in Etymologies but abandoned by Tolkien and replaced by MALTA / MALDA, also in Etymologies.

On the other hand, "piece of silver" is TELPILIN , gerund of TELPË = "silver" --> "money"

why does "piece of gold" is not KULUILIN (gerund of KULU) or MALTASTA (suffix. {verbal noun} for MALTA) ?