reffering to the number "four".
reffering to the word "for".

Bad english.

'Fuck off', abbreviated for use in chatrooms, email or text meassages.
'Fuck', taken from 'mofo', which in turn is an abbreviation of 'motherfucker'.
'For', most common used in the phrase 'fo sure'/ 'fo shizzle', both meaning 'for sure', a complicated way of saying 'yes'.

Fo can mean the following
1. Slang for the number "four"

2. Slang for "for"

3. Slang for info, or information

the number between 3 and 5

1. Anything you perceive to be bad or negative
2. An ugly or unattractive person- adj, noun
3. an insult used in joking around with a friend

1. Gangsta shortening of "for"

2. The number following tree

3. Short for mofo, which in turn is short for motherfucker.