A more publicly usable
alternative for the word Fucking.
Generally used as an Adjective, like to
emphasize something.
The word Fuck is refferred to as the F-Word generally,
so "Fucking" would be F-Word with an "ing",
so that would be F-ing, and this is pronounced as "Ef-ing" and this evolved into "Effing" or "Efing" being an
alternative for Fucking.
The "g" in "Effing" isn't required to get the desired pronounciation, so it is omitted, giving our result of "Effin" or "F-in"