Blend of thank you and fuck you. Used best when talking to those you really couldn't care less about. Example: Snooty clerk at high-end store *finally* asks if you need help--*after* you've been in the store for 20 minutes, Are we doing okay here? You reply, Yes, fank you. I was just leaving.
FANK YOU
Meaning of FANK YOU in English
Slang English vocab. Английский сленговый словарь. 2012