Where does “walled plain” come from?

walled plain (English) comes from English plain, from Middle English pleyn, from Anglo-Norman pleyn, from Old French playn, from Old French plain, from Latin plēnus, from Proto-Italic plēnos, from Proto-Indo-European pl̥h₁nós — to fill.

walled plain (English): A large impact crater that has a relatively flat floor, surrounded by a wall

Definitions

  1. A large impact crater that has a relatively flat floor, surrounded by a wall

Ancestry of “walled plain”, step by step

walled plain 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 walled

StepLanguageWordMeaning
1EnglishwalledPertaining to a wall; surrounded by a wall;...
Every word from Proto-Indo-European pleh₁-