From a (as a negative particle) and a derivative of saleuo; unshaken, i.e. (by implication) immovable (figuratively) -- which cannot be moved, unmovable.
KJV: And falling into a place where two seas met, they ran the ship aground; and the forepart stuck fast, and remained unmoveable, but the hinder part was broken with the violence of the waves.
NASB: But striking a reef where two seas met, they ran the vessel aground; and the prow stuck fast and remained immovable, but the stern began to be broken up by the force of the waves.
KJV: Wherefore we receiving a kingdom which cannot be moved, let us have grace, whereby we may serve God acceptably with reverence and godly fear:
NASB: Therefore, since we receive a kingdom which cannot be shaken, let us show gratitude, by which we may offer to God an acceptable service with reverence and awe;