The word 'unstoppable' is a modern English formation built from native Germanic and borrowed Latinate elements. Its core, 'stop,' originates from Old English stoppian, meaning to block or close an opening, which itself may have been influenced by Latin stuppāre, "to plug with tow." The negative prefix 'un-,' one of the oldest and most productive in English, is directly from Proto-Germanic. The suffix '-able' entered English via Old French from Latin -abilis, a marker of capability. Thus, the literal construction "not capable of being stopped" perfectly captures its modern sense of an irresistible force or inevitable progression, showcasing English's hybrid capacity for logical word-building.

Structure: un (not) + stop (to cease) + able (capable of) - un: A prefix of Germanic origin (Old English un-), meaning "not." It functions as a negative particle. - stop: A verb of Germanic origin (from Old English stoppian, "to block up, close"), functioning as the core lexical root. - able: A suffix of Latin origin (via Old French -able, from Latin -abilis), meaning "capable of, fit for." It forms adjectives.