the word tremulous originates from the latin verb tremere, which means 'to shake, tremble'. this latin root is itself traceable to the proto-indo-european base trem-, conveying the core concept of trembling. the suffix -ulous, derived from latin -ulosus, is added to nouns or verb stems to form adjectives indicating a tendency or abundance of a quality. therefore, the literal construction 'prone to shaking' evolved naturally into the modern english meanings describing both a physical quiver and a metaphorical state of nervousness or timidity.

Structure: trem (shake) + ulous (full of, prone to) trem is from latin tremere, meaning 'to shake'. ulous is an adjective-forming suffix from latin -ulosus, meaning 'full of, prone to'.