1851, "piece of bric-a-brac from the Far East," a shortening of curiosity (n.) in the "object of interest" sense (1640s). Extended by 1890s to rare or interesting bric-a-brac from anywhere.
Curioso (1650s) was a 17c.-18c. word for "one who is curious" (about science, art, etc.) also "one who admires or collects curiosities," from Italian curioso "curious person."