The form helta- in the Etymologies is a misreading according to VT/46:14
Adûnaic
-at
suffix. dual suffix
Black Speech
-at
suffix. verb ending (like a participle)
u
preposition. to
Noldorin
-ath
suffix. collective or group plural
heltha-
verb. to strip
Primitive elvish
-ata
suffix. numerative dual ending
an
preposition. to
Sindarin
-ath
suffix. collective or group plural
-ath
suffix. group plural embracing all things of the same name
an
to
(prep.) an (+ nasal mutation), with article ni "to the" (+ nasal mutation in plural).
an
to
(adverbial prefix) an-. 3)
-rim
suffix. collective or group plural
an
preposition. to, towards, for
With suffixed article and elision in aglar'ni Pheriannath
an
to
_ prep. _to, for. naur an edraith ammen! 'fire [be] for rescue/saving for us'. aglar an|i Pheriannath 'glory to all the Halflings'.
na
to
e _ prep. _to, towards (of spacetime). n' before vowels. >> nan 2
na
preposition. to
prep. to Na-chaered palan-díriel lit. "To-distance (remote) after-gazing" >> na-chaered, nan 2
Quenya
-nna
to
-n (1) dative ending, originating as a reduced form of -nă "to", related to the allative ending -nna (VT49:14). Attested in nin, men, ten, enyalien, Erun, airefëan, tárin, yondon (q.v.) and also added to the English name Elaine (Elainen) in a book dedication to Elaine Griffiths (VT49:40). The longer dative ending -na is also attested in connection with some pronouns, such as sena, téna, véna (q.v.), also in the noun mariéna from márië "goodness" (PE17:59). Pl. -in (as in hínin, see hína), partitive pl. -lin, dual -nt (Plotz). The preposition ana (#1) is said to be used "when purely dative formula is required" (PE17:147), perhaps meaning that it can replace the dative ending, e.g. *ana Eru instead of Erun for "to God". In some of Tolkiens earlier material, the ending -n (or -en) expressed genitive rather than dative, but he later decided that the genitive ending was to be -o (cf. such a revision as Yénië Valinóren becoming Yénië Valinórëo, MR:200).
-nna
to, at, upon
-nna "to, at, upon", allative ending, originating from -na "to" with fortified n, VT49:14. Attested in cilyanna, coraryanna, Endorenna, Elendilenna, númenórenna, parma-restalyanna, rénna, senna, tielyanna, q.v. If a noun ends in -n already, the ending -nna merges with it, as in Amanna, formenna, Elenna, númenna, rómenna as the allative forms of Aman, formen, elen, númen, rómen (q.v.). Plural -nnar in mannar, valannar, q.v.
ana
to
ana (1) prep. "to" (VT49:35), "as preposition _ana _is used when purely _dative formula is required" (PE17:147), perhaps meaning that the preposition ana can be used instead of the dative ending -n (#1, q.v.) Also as prefix: ana- "to, towards" (NĀ1); an (q.v.) is used with this meaning in one source (PE17:127)_
na
to, towards
na (2) prep. "to, towards", possibly obsoleted by #1 above; for clarity writers may use the synonym ana instead (NĀ1). Originally, Tolkien glossed na as "at, by, near"; the new meaning entered together with the synonyms an, ana (VT45:36).
Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!
Doriathrin
-ath
noun. collective plural
A class plural suffix, identical to N. -ath (PE21/57). It is possible this suffix was also used as (and was perhaps inspired by) the Gnomish general plural suffix -th.
Middle Primitive Elvish
-asta
suffix. collective plural
-d
suffix. allative
Early Quenya
-nta
suffix. to, at, towards; allative suffix
lenqelénu
noun. (daddy) long-legs
Gnomish
to
proper name. To
The suffix for dual nouns in Adûnaic, with the a lengthened to â in subjective duals (SD/428-430). In later (Exilic?) Adûnaic, the â was long in all cases (SD/431). See the entry on dual nouns for further details. Carl Hostetter and Patrick Wynne suggested (AAD/11) that -at is derived from the same Primitive Elvish form ✶-ata as the Quenya dual.