Green’s Dictionary of Slang

1. pregnant.

1855

Life in Boston & N.Y. (Boston, MA) 14 Apr. n.p.: Cully says it isn’t certain that she is fixed yet, and [...] he isn’t the only one who has had a finger in the pie.

2. (US) armed; carrying a weapon.

1872		‘Mark Twain’ Roughing It 57: When the ‘divison-agent’ issued an order to one of these parties he did it with the full understanding that he might have to enforce it with a navy six-shooter, and so he always went ‘fixed.’.
1890		Salt Lake Herald (UT) 24 Sept. 2/1: He stepped back and drew his gun. I said, ‘Don’t do that. I am as well fixed as you are.’ There was a revolver under the counter.