Where does “onrush” come from?

Onrush derives from Middle English on- combined with Old English and-, ultimately tracing through Proto-Indo-European h₂ent- meaning "being" or "entity," blended with ḱers- and ano-.

onrush (English): A forceful rush or flow forward; An aggressive...

Definitions

  1. A forceful rush or flow forward; An aggressive...

Ancestry of “onrush”, step by step

onrush traces back through two separate lines of ancestry.

via English on

StepLanguageWordMeaning
1EnglishonIn the state of being active, functioning or...
2Middle Englishonon, in; on; Alternative form of oon
3Old Englishonon, in, at, among; from
4Proto-West Germanicanaon
5Proto-Germanic*an—
6Proto-Germanicanaon, at; on, onto; ana
7Proto-Indo-Europeanh₂en-on, onto

via English rush

StepLanguageWordMeaning
1EnglishrushAny of several stiff plants of the genus...
2Middle Englishruschen—
3Old Englishhrysċanto jolt, startle
4Proto-Germanichurskijanąto be quick; rush; drive
5Proto-Germanichurskazfast; quick; lively
6Proto-Indo-Europeanḱers-to run
Every word from Proto-Indo-European h₂en- →
onrush — Etymology, Origin & Word History | Etymology Explorer