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!

Qenya 

ondaro

adverb. *for the very same reason

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”.