Where does “erstwhile” come from?

Erstwhile derives from Old English hwīl and ǣresta, tracing through Proto-Germanic airist and ultimately to Proto-Indo-European roots kʷyeh₁-, -istHos, -tós, and -yoss meaning superlative degree.

erstwhile (English): Formerly; in the past; Former, previous;...

Definitions

  1. Formerly; in the past; Former, previous;...

Ancestry of “erstwhile”, step by step

erstwhile traces back through two separate lines of ancestry.

via English while

StepLanguageWordMeaning
1EnglishwhileAn uncertain duration of time, a period of time;...
2Middle Englishwhylewhile
3Old Englishhwīltime; while; while; time, while
4Proto-West Germanichwīluperiod of rest, pause; time, period of time,...
5Proto-Germanichwīlōtime, period of time, while; period of rest,...
6Proto-Indo-Europeankʷyeh₁-to rest; rest, peace

via English erst

StepLanguageWordMeaning
1EnglisherstFirst
2Middle Englisherste
3Old Englishǣrestafirst
4Proto-Germanicairistearliest, at first; superlative degree of *airi
5Proto-Germanicairiearly
6Proto-Germanicairizearlier, before; comparative degree of *airi
Every word from Proto-Indo-European kʷyeh₁-Every word from Proto-Germanic hwīlōEvery word from Proto-West Germanic hwīlu