√DER root. “hard, difficult”
A root in linguistic notes from 1959 used for the sense “hard, difficult” in Sindarin because other roots like √GUR > S. gor- gained a very negative sense due to collision with the roots √ÑGOR “horror” and √ÑGUR “death” (PE17/154). Tolkien first gave this root as √DIR before switching it to √DER. There is no indication of its use in Quenya, so it is probably a Sindarin-only innovation.
References ✧ PE17/151, 154