Qenya
on-
prefix. the same (oneness, uniqueness), identical
ondaro
adverb. *for the very same reason
anta-
verb. to give
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!
The correlative ᴹQ. ondaro appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/112), a combination of ᴹQ. on- “same” and ᴹQ. -ro “reason”.
Neo-Quenya: For purposes of Neo-Quenya I would update this to ᴺQ. imaro “for the very same reason” using im- “same”.