A verb appearing as dœlio > delio “conceal” in The Etymologies of the 1930s under the root ᴹ√DUL “hide, conceal” (Ety/DUL; EtyAC/DUL). Its modern form indicates that first short u > o, and then this o underwent i-affection > œ > e.
Neo-Sindarin: These phonological developments may present some problems with Tolkien’s later ideas of how u > o in Sindarin. To avoid those complications, I recommend using N. doltha- “conceal” instead.
A verb for “conceal” in The Etymologies of the 1930s under the root ᴹ√DUL “hide, conceal” (Ety/DUL).