Based on the police (and military) call sign alphabet where "Whisky" is "W", "Tango" is "T", and "Foxtrot" is "F". For use in situations where swearing would be unwise, such as at work or around minors.
Code words for WTF, an internet abbreviation that actually stands for "What The F*ck" (WTF..does that mean? ..is he doing? .. etc) If you don't want to refer to the offensive word in mixed company, you state the "code" instead.