Where does “জেঠীআই” come from?

জেঠীআই (Assamese) comes from Assamese জেঠী, from Sanskrit ज्येष्ठ, from Proto-Indo-Iranian *ȷ́yáHištʰas.

Ancestry of “জেঠীআই”, step by step

জেঠীআই traces back through two separate lines of ancestry.

via Assamese জেঠী

StepLanguageWordMeaning
1Assameseজেঠীcommon house gecko, house lizard (Hemidactylus frenatus)
2Sanskritज्येष्ठmost excellent, pre-eminent, first, chief, best,...
3Proto-Indo-Iranian*ȷ́yáHištʰas

via Assamese আই

StepLanguageWordMeaning
1Assameseআইmother, mom
Every word from Proto-Indo-Iranian *ȷ́yáHištʰasEvery word from Sanskrit ज्येष्ठEvery word from Assamese জেঠী