This word is shortened down to from Pakistani to Paki (however, this word is usually generalised to mean anyone is from the middle east eg afgan, iraqi.)
This word is usually taken as an offence by muslims, although users of the word mean no harm, they just use the word to save shouting Pakistani and to save breath.
(1): Pakistan person - Pakistani - Paki
(2): "You bloody paki!"
(3): "Have you seen that Pakistani over there?"
(4): "Have you seen that Paki over there?"