Language is what people use to communicate, not what's written in the books. It's fluid, and adapts to requirements as the requirements change.

Would it be better if they invented a completely new word, with no clue as to what it means, rather than adapt an existing language structure to their purpose, which everyone understands immediately (even if they get grumpy at it)?

yes, but don't blame OP for it. this is effectively a term of art in their field.