Where does “floodplain” come from?

Floodplain derives from English flood and plain, where plain comes from Old French plain, Latin planum meaning flat, and ultimately Proto-Indo-European pleh₁-.

floodplain (English): An alluvial plain that may or may not experience...

Definitions

  1. An alluvial plain that may or may not experience...

Ancestry of “floodplain”, step by step

floodplain traces back through two separate lines of ancestry.

via English plain

StepLanguageWordMeaning
1EnglishplainFlat, level; Simple; Obvious
2Middle Englishpleynclear; unambiguous
3Anglo-NormanpleynAlternative form of plein
4Old Frenchplayn
5Old Frenchplainfull; plain; flat
6Latinplēnusfull; filled; complete
7Proto-Italicplēnosfull
8Proto-Indo-Europeanpl̥h₁nósfull
9Proto-Indo-Europeanpleh₁-to fill

via English flood

StepLanguageWordMeaning
1EnglishfloodA overflow of water from a lake or other body of...
2Middle EnglishflodA waterbody or water in general; A flood; a...
3Old Englishflōdriver, flood
4Proto-West Germanicflōduriver; flood
5Proto-Germanicflōduzriver; flood
6Proto-Indo-Europeanplōw-to flow, swim; to pour, wash
7Proto-Indo-Europeanplew-to fly, flow, run
Every word from Proto-Indo-European pleh₁-