Quivering comes from quiver + -ing; quiver ('to tremble') is probably imitative or a variant of quaver, perhaps related to Middle English quaveren and ultimately of Germanic origin. Older glosses in the chain include "to tremble", which help explain the semantic range of the modern word. Morphologically, quivering is best read as compound, suffixal formation, and imitative formation, yielding an English adjective shaped by both form history and later usage. In current English it functions as an adjective, with the sense "trembling or shaking with a slight rapid motion". related forms include quiver and quaver. The result is an English adjective whose etymology preserves the older forms while supporting the word's specialized modern meaning.