Where does “இருபத்தொன்று” come from?

இருபத்தொன்று (Tamil) comes from Tamil இரு, from Proto-Dravidian iru, from Proto-Dravidian *ir-aṇ-ṭu.

Ancestry of “இருபத்தொன்று”, step by step

இருபத்தொன்று traces back through 3 separate lines of ancestry.

via Tamil இரு

StepLanguageWordMeaning
1Tamilஇருto be, exist, be present
2Proto-Dravidianirutwo
3Proto-Dravidian*ir-aṇ-ṭu—

via Tamil ஒன்று

StepLanguageWordMeaning
1Tamilஒன்றுone
2Proto-Dravidianonṯuone

via Tamil பத்து

StepLanguageWordMeaning
1Tamilபத்துten (numeral: ௰)
Every word from Proto-Dravidian *ir-aṇ-ṭu →Every word from Proto-Dravidian iru →Every word from Tamil இரு →