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).