Why did they put the x on Malcolm X?

i nthe time of black slave, a slave took the last name of their owner. malcom x became independent of that when he gave up his slave name for the variable x which represents his true last name that he lost to the slave owner.

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Above is a different answer from what I heard on a different website. Malcolm X isn't his REAL name. The Malcolm was given to him by one of his teachers and the X is an unknown thing in math, so that's how he made his name... Malcolm 'Unknown'