Green’s Dictionary of Slang

1. well-dressed.

1972		Andrews & Dickens Voices from the Big House 29: You are without a doubt the hooked-up-est dude I have ever seen.
1986		Eble Campus Sl. Mar. 6: hook-up – match clothing: Oh you’re hooked up today! What’s the occasion?
1992		G.P. Pelecanos Firing Offense 185: I got dressed that morning, real sharp. [...] I was so hooked up, I was proud’.

2. intelligent, culturally aware.

1994		N. McCall Makes Me Wanna Holler (1995) 248: I’d entered college [...] and was now getting ‘hooked up’ as we said on the block.
1997		(con. 1970s) G. Pelecanos King Suckerman (1998) 109: ‘You’ve got quite a selection [i.e. of books].’ ‘Yeah, I’m hooked up.’.