Where does “ghost chili pepper” come from?

ghost chili pepper (English) comes from English ghost, from Middle English gost, from Old English gāst, from Proto-West Germanic gaist, from Proto-Germanic gaistaz, from Proto-Indo-European ǵʰeysd- — anger, agitation.

Ancestry of “ghost chili pepper”, step by step

ghost chili pepper traces back through two separate lines of ancestry.

via English ghost

StepLanguageWordMeaning
1EnglishghostThe spirit; the soul of man; The disembodied...
2Middle Englishgosta spiritual being; angel, devil, spirit; soul of...
3Old Englishgāstbreath, soul, spirit, ghost, being
4Proto-West Germanicgaistghost, spirit
5Proto-Germanicgaistazterror, fear; spirit, ghost; mind
6Proto-Indo-Europeanǵʰeysd-anger, agitation

via Assamese ভূত-জলকীয়া

StepLanguageWordMeaning
1Assameseভূত-জলকীয়াbhut jolokia
2Assameseভূতghost
3Sanskritभूतbeen
4Proto-Indo-IranianbʰuHtásbecome, been
5Proto-Indo-EuropeanbʰuH-tó-s
6Proto-Indo-EuropeanbʰuH-to become, grow, appear
Every word from Proto-Indo-European ǵʰeysd-Every word from Proto-Germanic gaistazEvery word from Proto-West Germanic gaist