passerby

The word 'passerby' is a transparent English compound formed from existing native elements. Its first element, 'passer', originates from the Latin 'passus' (a step, pace), which entered English via Old French, acquiring the agent suffix '-er' to mean 'one who passes'. The second element, 'by', is a fundamental Old English adverb and preposition denoting proximity. The compound's literal logic, "one who passes near," directly and vividly captures the modern meaning of a transient, incidental witness to an event. It exemplifies how English readily combines borrowed and native morphemes to create precise, descriptive terms for everyday social phenomena.

Structure: passer (one who passes) + by (near) - passer: From the English verb 'pass' (Middle English, from Old French 'passer', from Latin 'passus', meaning 'step, pace') + the agentive suffix '-er', denoting a person who performs the action. - by: From Old English 'bī', meaning 'near, at, during'. In this compound, it functions as an adverb meaning 'past, alongside'.