The word "steerable" is a modern English formation built upon the ancient verb "steer," which traces back to the Proto-Germanic steurijaną, itself derived from the Proto-Indo-European root steu-ro-, meaning "to push, stick, knock, beat," a concept related to applying force to control direction. The suffix "-able," entering English via Old French from Latin -abilis, is a productive morpheme that converts verbs into adjectives denoting capacity or susceptibility. Thus, the literal construction "capable of being steered" logically yields the modern technical and general sense of an object or system designed to be guided or have its course altered.

Structure: steer (to guide) + able (capable of) steer: From Old English stieran, meaning "to guide, direct, govern." Its functional role is the core verb root. able: From Latin -abilis, a suffix forming adjectives meaning "capable of, fit for, tending to." Its functional role is a derivational suffix.