The "B" slur (please do not confuse with bitch) comes from the noun bean and the suffix "
er". This is how some
people refer to central Americans who live abroad illegally. Though it is most of the times used with black coloured
people.
-Hey,
sup, dude?
-Nothing much, dick. I just came across a beaner...
-What'd you do?
-I said, "Hey, you, black coloured
motherfucker, who eats beans for breakfast, dinner and
tea, come here!", gave him a beans tin and told him to learn some proper English. His English sucks!