See also the preposition ned , and the noun ened for a discussion of this form
Noldorin
minna-
verb. to enter
di
preposition. in
ne-
prefix. in
nedh-
prefix. in, inside, mid-
neledh-
verb. to enter
Hammond and Scull apparently understand this word as a derivative of neledh "three", hence their translation neledh neledhi "three by three". However, we have shown in Hiswelókë (third issue, pp. 74-78) that this word is conceivably a verb derived from LED "to go". The prefix ne- also occurs in nestegi "to insert, stick in"
A prefix for “in” implied by the verb N. nestag- “insert” from The Etymologies of the 1930s (Ety/STAK). It was probably derived from primitive ᴹ✶ndē̆- “in, inside” based on the root ᴹ√NĒ̆, but this root and its derivatives were deleted (EtyAC/NĒ̆).
Neo-Sindarin: Despite the deletion of its root, I think it is worth retaining ne- “in” for purposes of Neo-Sindarin.