Green’s Dictionary of Slang

1. (US) an outfit.

1844

‘Jonathan Slick’ High Life in N.Y. I 195: If you want to slick up, had’t you better take the new fix, it’ll look a good deal more scrumptious?

2. (Aus.) fitness, condition.

1902

Bulletin (Sydney) 18 Oct. 24/2: Glasson hadn’t ‘fix’ enough to fight two rounds, and shaped like a novice, despite his alleged record of successes in Africa. [...] [T]he Maori ‘chucked it,’ dog-tired and done, on the groundless assertion that Lynch had struck him ‘in holts’.