Any Polish jokes made up by the group you mention would doubtless not be in English. Also, I've never heard a Pole say 'Polock' (though I rarely hear them speak English these days) - I suspect you've never heard the word in Poland either.
Are you confusing it with Polak? Though remember, that's a Polish rather than an English word.
Are you confusing it with Polak? Though remember, that's a Polish rather than an English word.