Ada Lovelace, English mathematician, an associate of Charles Babbage, for whose digital computer prototype, the Analytical Engine, she created a program in 1843. She has been called the first computer programmer. Ada Lovelace Day, the second Tuesday in October, honors women’s contributions to science and technology.
It’s also to differentiate the physical hardware from e.g. a VM with a given chunk of compute that you’ve rented from a cloud provider.
In other words, one “machine” may host more than one “system” or “instance”, so it’s a useful bit of differentiation on that end as well.