Synonyms for once:
bygone, immemorial, ago, hitherto, Beforetime, Whilom, Aforetime.
previously, unrepeatable, one-off, backward, already, earlier.
late, old, previous.
in the past; occurred one time only (adverb)
before, earlier, bygone, old, erstwhile, late, sometime, quondam, already, back, Whilom, previously, at one time, formerly.
Sense 2 (noun)
Sense 3 (noun)
already, Beforetime, isolated, before, previously, unrepeatable, Aforetime, one shot, one-off, earlier.
Usage examples for once:
- "Martin Pippin in the Apple Orchard",
- "The Boy Scouts Book of Stories",
- "The Happiest Time of Their Lives",
Alice Duer Miller.