Green’s Dictionary of Slang

weird adj.

(orig. UK society) wonderful, excellent.

1905		‘Doss Chiderdoss’ ‘Off the Mark’ Sporting Times 22 Apr. 1/3: She called that being sober, when of course ’twas proof most weird / I was absolutely blue blind to the wide!
1958		PADS Nov. 41–2: Such terms as crazy, weird, wild, and nervous, all used to express favorable responses to music, are adaptations levelled against the bop musicians. Since they knew the music which people called ‘crazy’ was actually good, they took over the word in a good sense.

SE in slang uses

In compounds

weird-ass (adj.) [-ass sfx]

(US) strange, eccentric, mad.

1967		J. Rechy Numbers (1968) 104: Crazy bastard! Weird-ass fucker!
1998		P. Cornwell Point of Origin (1999) 26: You’re talking to the expert in weird-ass names and how they fit the squirrels who have them.