twat (____). low slang. Also 8 twait, 20 twot(t. [Of obscure origin.] 1. (See quot. 1727.) Erroneously used (after quot. 1660) by Browning Pippa Passes iv. ii. 96 under the impression that it denoted some part of a nun's attire.
the SOED denotes that the English English meaning is the same as "fanny" and the American English meaning has the same meaning as "fanny" there.