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!