That's the funny thing - in almost all contexts I've seen the "master/slave" terminology, it's not actually technically clear.
In some contexts (e.g. Jenkins), a "master" tells the "slave" what to do and the "slave" does it. This at least is plausibly connected to the real-world meanings of the term, although given that the "slave" can start and stop work at any time and the "master" needs to accommodate that, the analogy isn't great. "Coordinator/worker" works well here.
In some contexts (e.g., MySQL), a "master" sends a copy of all its work to the "slave," and both of them execute it. The "slave" stands ready to replace the "master" if the "master" becomes unavailable, and usually at that point the "master" becomes the new "slave" once it catches up. This makes no sense. "Primary/replica" works well here.
In some contexts (e.g., network device bonding, and, I think, ZFS), a "master" is a logical construct, consisting of multiple physical "slaves". All interactions with the "master" are actually algorithmically sent to one or more "slaves," and if all the "slaves" are offline, there's no "master" left. This, also, makes no sense. Terms that would make sense include things like "bond device/bonded member" (the members being bonded to each other), "logical volume/physical volume", etc. In this pull request they seem to use "dependency."
In some contexts (e.g. disk drives), the "master" and "slave" are both devices that provide the same type of service to the host, but the "slave" connects to the "master" instead of directly to the host, and while the "master" is communicating, the "slave" can't. This, also, makes no sense. "Primary/secondary" works well here.
In pseudoterminals, the "master" is a limited API to the PTY object, held by the terminal emulator, which copies text to the screen, interpreters rendering commands, and sends input. The "slave" is a more featureful API to the same PTY object, held by the shell / the command under execution, which does what it wants. This, also, makes no sense. I don't know of a standard term here, but I'd sort of suggest "monitor" and "application" (or perhaps "monitor" and "session" if you want to keep the initials).
All of these are different uses, and you can't generally map one to another. For instance, if you're used to a database where "master/slave" is used in the primary/replica sense, and you see a database where the "master" just coordinates requests for work and all actual data is sent to/from some "slave," your knowledge of primary/replica architecture is misleading here.