Same name, similar-looking formula, two completely different physical quantities — one about spinning mass, the other about a shape's resistance to bending.
Few phrases in engineering cause more quiet confusion than "moment of inertia." Say it in a dynamics class and everyone pictures a spinning flywheel. Say it in a mechanics of materials class and everyone pictures an I-beam cross-section. Both are correct — and both are talking about entirely different things that happen to share a name and a mathematical family resemblance. Confuse them, and you don't just get a wrong number; you get a number with the wrong units doing a job it was never built for.