Qenya
at(a)-
prefix. back, again, re-
tanta
adjective. double
atta
cardinal. two
opto
noun. back
waryallume
adverb. *at a different time
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!
A word (noun?) translated as “back” in notes on The Feanorian Alphabet from the 1940s (PE22/50).
Conceptual Development: The Qenya Lexicon of the 1910s had a noun ᴱQ. ponte “back, rear” under the early root ᴱ√POT-I (QL/75). Early Noldorin word-lists of the 1920s had ᴱQ. ponte as the equivalent of ᴱN. bón “back” (PE13/139), while Early Qenya word-lists from this same period had ᴱQ. ponte “back” (PE16/136).
Neo-Quenya: In Tolkien’s later writings, the root √OPO was used for “in front” (PE22/168; VT49/32), so I would replace these early “back” words with a neologism ᴺQ. catta “back” based on the later preposition Q. ca(ta) “behind, at back (of place)”.