Throughout my education in computer science, I feel like I've heard the terms "modulo" and "modulus" used interchangeably. It looks like even Wikipedia claims that "modulo" is "sometimes called 'modulus'" (see the first sentence of the page on 'modulo').
I've looked into this issue a little and it seems that "modulo" finds singular use in modular arithmetic (e.g. "19 and 64 are congruent modulo 5"). In addition, I've seen the symbol
% be referred to as "modulo."
Meanwhile, "modulus" appears to have several definitions, including "absolute value" and "constant factor" as well as referring to the "5" in "modulo 5."
Is it ever correct to use these terms interchangeably in the context of computer science? Are they simply different types of words that represent the same idea (such as "run" and "runner")? Are there important differences in other disciplines?
Bonus: Etymologically, what gave rise to these two terms?