immobility comes from Latin immobilitas, from immobilis ('immovable'), from in- ('not') + mobilis ('movable'). Morphologically, the prefixed shape matters: the initial element belongs to the recorded formation and helps explain the modern form's surface analysis. In present English, the noun sense is "the state of being unable to move or be moved", so the historical development ends in a clearly identifiable modern dictionary use. The same base also appears in related forms such as immobile, mobile, mobility, and immobilize. Its semantic neighborhood includes stillness, motionlessness, stasis, and fixity, which helps locate the modern sense without adding a separate etymological claim. The named historical forms include Latin immobilitas and Latin movere.