A correlative combination appearing as linallume or lillume in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/110), a combination of ᴹQ. li(n)- “several, many” and ᴹQ. -llume “times”.
Qenya
-llume
suffix. time, time, [ᴱQ.] times
o(na)llume
adverb. at or during exactly the same time
li(na)llume
adverb. *many a time, *many a time, often, sometimes
-n(an)
suffix. time
The correlatives ᴹQ. ollume or onallume “at or during exactly the same time” appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/100, 110), a combination of ᴹQ. on- “same” and ᴹQ. -llume “time”.
Neo-Quenya: For purposes of Neo-Quenya I would update this to ᴺQ. imallumë “at the very same time” using im- “same”.