Micturition is the medical term for the act of passing urine - either voluntarily or involuntarily. These days, "urination" is used in polite common parlance, and various other words are used colloquially.
My parents used to refer to my penis as my "micky", and I suspect this was derived from the word micturition. No doubt their parents used the word, as medical terms were used more frequently by the general public in Victorian times.
The phrase " taking the mick" is often ascribed to cockney rhyming slang, and is an abbreviation of taking the Micky Bliss. However, nobody seem to know who Micky Bliss was, so I believe that this is a convenient fabrication, and the "mick" is a diminutive of micturition.
So what do you guys think? I haven't seen anybody else propound this theory.