phrase is not new; the full phrase is "to take the Mickey (out of someone)"
been using this
figure of speech for decades, if not centuries. A "Mickey" of course, is a "Mick": a pejorative, racist
term for an Irishman (so nicknamed because so many Irish
with Mc- or Mac-) It is a common
stereotype, in both the UK and USA, that Irish
volatile tempers, like to brawl, and make good boxers. So, To "take the Mickey (out of someone)" means to take the fight, the vigor, the gravity, the self-importance out of them, by mocking them, usually
in a very subtle way.
Headmaster: "...so I expect you boys to comport yourself with the full dignity
of this establishment of secondary learning."
Student: "Oh yes, we will sir. We'll even wear
our school blazers to bed."
Headmaster: "If I didn't know
better, I'd think you were
trying to take the Mickey out of me!"