Wordorigins.org

This word for the female genitalia dates back to the Middle English period, c.1325. It’s exact origin is unknown, but is related to the Old Norse kunta, a word with cognates in several other Germanic languages. From the Proverbs of Hendyng, a manuscript from sometime before 1325:

Ȝeue þi cunte to cunnig and craue affetir wedding.
(Give your cunt wisely and ask for what is due after the wedding.)