Origins of 'sick' meaning noteworthy, admirable, exceptional, etc.

[Martin Kaminer]

My son chose his 11th birthday to ask me about this. Clearly words
developing slang meanings opposite to their original definitions is common
in many languages but I couldn't find anything specific about the phenomenon
when I poked around online. I imagine there's even a term for it.
 Regardless any pointers appreciated, those specific to slang uses of the
words 'sick' or 'ill' all the more so.

Much thanks.

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