[nickpsecurity]

Systems are relationships between input from the environment, algorithms/functions to process it, and output to the environment. Basically programs at a high-level representation. Systems analysis, design, and implementation started with basic control systems far as I can tell. At some point, there was a distinction between "systems" and "application" programming made by whoever. Original meaning of the term covered all programming where you then picked tools (eg languages) best suited for particular task.

Go's predecessors... Oberon-2, C, and Limbo... were two languages for OS's plus a distributed, systems language. Go's core is the first two with last being mainly for concurrency IIRC. That with ability to do unsafe stuff makes me think of Go as a systems language used mainly for regular applications.