To be hep on X

[Mark A. Mandel]

Suzanne writes:
>>>

I recently heard this expression, which a Google search reveals to be
marginal but definitely present in colloquial writing, especially blogs and
discussion groups.

        [...]

Some of the tokens I found suggest it might also be used to mean "worked up
about [a contentious issue]", "obsessed with" or just "enthusiastic about".
<<<

That sounds like (a confusion with) "het up (about smth)". MW online:

One entry found for het up.
Main Entry: het up
Pronunciation: 'het-'&p
Function: adjective
Etymology: het, dialect past of heat
: highly excited : UPSET

m a m