Where does “ağcaqayın” come from?

ağcaqayın (Azerbaijani) comes from Azerbaijani qayın, from Proto-Turkic *kadïŋ.

Ancestry of “ağcaqayın”, step by step

ağcaqayın traces back through two separate lines of ancestry.

via Azerbaijani qayın

StepLanguageWordMeaning
1Azerbaijaniqayınbrother-in-law, specifically, the brother of one's spouse
2Proto-Turkic*kadïŋ—

via Azerbaijani ağca

StepLanguageWordMeaning
1Azerbaijaniağcamoney
Every word from Proto-Turkic *kadïŋ →Every word from Azerbaijani qayın →