Is there a word for an intentional misnomer?

If the intentional misnomer disparages something positive (as, arguably, calling a tall person Shorty does), it qualifies as a dysphemism. From The Oxford Companion to the English Language (1992):

DYSPHEMISM In rhetoric, the use of a negative or disparaging expression to describe something or someone, such as calling a Rolls-Royce a jalopy. A cruel or offensive dysphemism is a cacophemism.

Another candidate (though not quite so apt) from the same source is meiosis:

MEIOSIS In rhetoric, a kind of understatement that dismisses or belittles, especially by using terms that make something seem less significant than it really is or ought to be: for example, calling a serious wound a scratch, or a journalist a hack or a scribbler.

Antiphrasis! Sometimes conflated with litotes.

Antiphrasis

the usually ironic or humorous use of words in senses opposite to the generally accepted meanings (as in "this giant of 3 feet 4 inches")

[Merriam Webster]