Where does “below stairs” come from?

below stairs (English) comes from English stairs, from English stair, from Middle English steire, from Old English stǣġer, from Proto-Germanic staigriz, from Proto-Indo-European steyǵʰ- — to go.

Ancestry of “below stairs”, step by step

below stairs traces back through two separate lines of ancestry.

via English stairs

StepLanguageWordMeaning
1Englishstairsplural of stair; API pl; A contiguous set of...
2EnglishstairA single step in a staircase; A series of steps;...
3Middle Englishsteirestaircase, stairs; stair, step; ladder
4Old Englishstǣġerstair, staircase
5Proto-Germanicstaigrizscaffold, platform; stairs
6Proto-Indo-Europeansteyǵʰ-to go

via English below

StepLanguageWordMeaning
1EnglishbelowLower in spatial position than; Within the...
2Middle Englishbilooghe
Every word from Proto-Indo-European steyǵʰ-Every word from Proto-Germanic staigrizEvery word from Old English stǣġer
below stairs — Etymology, Origin & Word History | Etymology Explorer