Look in a physics text beyond the introductory level. You'll see mass, you'll see moment of inertia, but you'll never see "inertia" by itself. Inertia is a nice term used by sports announcers in describing what happens when an American football linesman meets an American football running back, or when describing why they think a football team that has won ten games straight will win again this weekend. Here's the problem: Does the announcer mean mass or momentum, or is he talking about something that has absolutely nothing to do with science?
Why use a term that's ambiguous when there are two perfectly good, unambiguous words that mean mass and momentum? (Hint: The words are "mass" and "momentum".)