Meaning

noun a disposition to remain inactive or inert

noun (physics) the tendency of a body to maintain its state of rest or uniform motion unless acted upon by an external force

originFrom Latin inertia (“lack of art or skill, inactivity, indolence”), from iners (“unskilled, inactive”), from in- (“without, not”) + ars (“skill, art”). Something close to the modern physics sense was first used in New Latin by Johannes Kepler.

Etymology from Wiktionary, CC BY-SA 3.0