Downpour comes from Middle English down- combined with Middle English pour, derived from Old English purian, with down- tracing through Old English dūne, adūne, and ofdūne to Proto-Germanic ab meaning away or off.
downpour (English): A heavy rain; To pour down; rain heavily
Definitions
A heavy rain; To pour down; rain heavily
Ancestry of “downpour”, step by step
downpour traces back through two separate lines of ancestry.