The adjective “aquiver” pairs the verb “quiver,” meaning “to shake or move with slight tremulous motion,” and the prefix “a-,” which adds the meaning of “in (such) a manner.” This pairing creates the adjective that describes literally being in a physical state of shaking, but it’s often used in a metaphorical sense to describe emotional tumult. While it sounds like a more archaic word construction, “aquiver” only came into English in 1864. It remains mostly a literary or poetic word — you won’t hear people use “aquiver” much in regular conversation.