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 

hrímaro

adverb. *for many reasons

The correlative ᴹQ. {hríro, hrimiro >>} hrímaro appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/112), a combination of ᴹQ. hrim- “many” and ᴹQ. -ro “reasons”.

Neo-Quenya: For purposes of Neo-Quenya I would adapt this to ᴺQ. rímaro “for many reasons” using rim- “many” to be more compatible with Tolkien’s later writings.

li(lí)ro

adverb. *for many reasons

A correlative combination appearing in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/112), a combination of ᴹQ. li(n)- “several, many” and ᴹQ. -ro “reasons”.