Between the years 1987 and 1995, Apple Computers, Inc produced a distribution of Unix for the 680×0-based Macintosh. Based on System V release 2.2, Apple Unix (A/UX) provided a familiar Macintosh Finder environment with the ability to run both Unix and Mac applications. While the two products share no code, A/UX was the “conceptual ancestor” of OS X.
(From: https://www.aux-penelope.com/index.htm)
Once I get a BlueSCSI or a larger HD in my Centris 650, I’m definitely going to install A/UX on a partition just for fun.