The form helta- in the Etymologies is a misreading according to VT/46:14
Noldorin
an-
prefix. with, by
an-
prefix. with, by
dae
noun. shadow (cast by an object or form), shade
rhofal
noun. pinion, great wing (of an eagle)
dîr
noun. man, referring to an adult male (elf, mortal, or of any other speaking race)
paur
noun. fist (often used to mean "hand", its chief use was in reference of the tighly closed hand, as in using an implement or a craft-tool, rather than to the fist used in punching)
talad
noun. an incline, slope
a-
prefix. intensive prefix
-(r)on
suffix. agental suffix
-or
suffix. agental suffix
dae
adverb. very
i
article. the
-on
suffix. agental suffix
heltha-
verb. to strip
i
definite article. the
i
definite article. who
lhû
noun. a time, occasion
na
preposition. with, by (also used as a genitive sign)
na
preposition. to, towards, at
A noun in The Etymologies of the 1930s glossed “shadow” derived from the root ᴹ√DAY of the same meaning (Ety/DAY). The original penciled version had {daer >>} dae, while the inked version had daew “shadow (cast by an object or form)” and Dae “shade” (EtyAC/DAY). It was most notably an element in the name N. Dor-Daedeloth “Land of the Shadow of Dread” (LR/120, 405). Christopher Tolkien had S. dae “shadow” in The Silmarillion appendix (SA/dae), but I suspect that was copied from The Etymologies. In later writings, Tolkien seems to have changed the initial element of Daedeloth to a variant of S. daer “great”, and its meaning from “Shadow of Dread” to “Great Dread” (WJ/183).