From Why start at x, y, z

The word modulus is used in different areas of mathematics with no apparent reason for the name or naming convention connection (that I can tell). For instance, in elementary number theory, modulus refers to the base number for a system of modular arithmetic, whereas in the study of real or complex numbers, the term modulus represents the absolute value of a number.

Of course none of this is to mention that modulus also refers to a genus of sea snails.