Rashid liked Giuse's spelling 'Mach' so much that it prevailed. Italian CMU engineer Dario Giuse later asked project leader Rick Rashid about the project's current title and received 'MUCK' as the answer, though not spelled out but just pronounced as IPA: which he, according to the Italian alphabet, wrote as Mach. While the developers, once during the naming phase, had to bike to lunch through rainy Pittsburgh's mud puddles, Tevanian joked the word 'muck' could serve as a backronym for their Multi- User (or Multiprocessor Universal) Communication Kernel. Another of the original Mach developers, Avie Tevanian, was formerly head of software at NeXT, then Chief Software Technology Officer at Apple Inc. The lead developer on the Mach project, Richard Rashid, has been working at Microsoft since 1991 he founded the Microsoft Research division.

Mach is the logical successor to Carnegie Mellon's Accent kernel. The Mach virtual memory management system was also adopted in 4.4BSD by the BSD developers at CSRG, and appears in modern BSD-derived Unix systems, such as FreeBSD. These include all using the XNU operating system kernel which incorporates an earlier non-microkernel Mach as a major component. Mach and its derivatives exist within a number of commercial operating systems. Mach was developed as a replacement for the kernel in the BSD version of Unix, so no new operating system would have to be designed around it. The project at Carnegie Mellon ran from 1985 to 1994, ending with Mach 3.0, which is a true microkernel.

Mach's derivatives are the basis of the operating system kernel in GNU Hurd and of Apple's XNU kernel used in macOS, iOS, iPadOS, tvOS, and watchOS.

However, not all versions of Mach are microkernels.

Mach is often mentioned as one of the earliest examples of a microkernel. Mach ( / m ɑː k/) is a kernel developed at Carnegie Mellon University by Richard Rashid and Avie Tevanian to support operating system research, primarily distributed and parallel computing.

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