Where does “half-plane” come from?

half-plane (English) comes from English plane, from Middle English plane, from Old French plane, from Latin platanus, from Greek πλάτανος, from Ancient Greek πλάτανος, from Ancient Greek πλατύς, from Proto-Indo-European pléth₂us — flat.

half-plane (English): Either half of an infinite plane

Definitions

  1. Either half of an infinite plane

Ancestry of “half-plane”, step by step

half-plane traces back through two separate lines of ancestry.

via English plane

StepLanguageWordMeaning
1EnglishplaneOf a surface: flat or level; A level or flat...
2Middle Englishplane
3Old Frenchplane
4Latinplatanusplanetree, sycamore
5Greekπλάτανοςplane tree
6Ancient Greekπλάτανοςplanetree
7Ancient Greekπλατύςwide, broad; flat, level; broad-shouldered
8Proto-Indo-Europeanpléth₂usflat, broad
9Proto-Indo-Europeanpleth₂-flat

via English half

StepLanguageWordMeaning
1EnglishhalfConsisting of a half; Consisting of some...
2Middle Englishhalfhalf
3Old Englishhealfside; half; partly
4Proto-Germanic*halb
5Proto-Germanichalbazhalf
6Proto-Indo-European(s)kelH-to cut; to split, to separate
7Proto-Indo-European(s)kel-to bend, crook; bent, crooked; leg, heel, knee,...
Every word from Proto-Indo-European pleth₂-Every word from Proto-Indo-European pléth₂usEvery word from Ancient Greek πλατύς