Where does “ஆவது” come from?

ஆவது (Tamil) comes from Tamil ஆ, from Old Tamil 𑀆, from Proto-Dravidian *ā — cow.

Ancestry of “ஆவது”, step by step

ஆவது traces back through two separate lines of ancestry.

via Tamil ஆ

StepLanguageWordMeaning
1TamilஆThe second vowel of Tamil, written in the Tamil script
2Old Tamil𑀆cow; the female of an ox
3Proto-Dravidian*ācow

via Tamil வது

StepLanguageWordMeaning
1Tamilவது—
Every word from Proto-Dravidian *ā →Every word from Old Tamil 𑀆 →Every word from Tamil ஆ →