A word glossed “dwelling underground, artificial cave or rockhewn hall” derived from the root √s-rot (PM/365 note #56), appearing in 1959 notes discussing the origin of the name of Felagund, which in that document was based on a Khuzdul name.
Quenya
hróta
dwelling underground, artificial cave or rockhewn hall
hróta
noun. dwelling underground, artificial cave or rockhewn hall
hróta noun "dwelling underground, artificial cave or rockhewn hall" (PM:365)