ᴺS. !madhren adj. “muddy” (Category: Mud, Mire)
A neologism coined by Paul Strack in 2018 specifically for Eldamo, an adjectival form of S. madha “mud”, inspired by G. ûgrin “muddy” the adjectival form of ûg from the 1910s. It would need to be a late Sindarin (re)formation rather than the phonetic evolution from ancient forms.