An illiterate pronunciation of the word "Think". Usually, someone of low socio economic background tend to use the letter "F" in all words spelt the letters "TH". There are also other words which are commonly used by such people. (Bruva)= Brother,(Wiv)= With. The list goes on.
Wat are ya finkin bout? Me bruva finks you feeved his holden an vat. Viss is heaps good ahy.