arriver comes from arrive (from Old French ariver, from Vulgar Latin *arripare 'to come to shore', from Latin ad- and ripa 'shore, riverbank') plus the agentive suffix -er. Morphologically, the word is transparent: -er is attached to the older base named in the history, so the modern form packages an inherited or borrowed stem inside a later English derivative. In modern use, the noun sense is "a person who arrives, especially one newly come to a place", which keeps the etymology connected to the word's present dictionary value rather than treating it as a merely historical label. The wider word family includes related English forms such as arrive, arrival, river, showing how the same base continues to support neighboring English vocabulary. The principal historical forms in the chain include Old French ariver, Latin ripa, which anchor the explanation in named linguistic material.