English
erewhile
From ere + while.
Proto-Indo-European *kʷyeh₁- ‘to rest’
…
Proto-Germanic *hwīlō ‘time’
Proto-West Germanic *hwīlu ‘period of rest’
Old English hwīl ‘while’
Middle English whyle
English while
Today it means
adv Some time ago; beforehand; formerly.
Language periods are conventional ranges, not dates for this word.
Etymograph / erewhile