passer-by

The word 'passer-by' is a transparent English compound formed from two native elements. The first part, 'passer', originates from the Latin 'passus' (a step, pace), which entered English via Old French and acquired the agentive suffix '-er' to denote "one who passes". The second element, 'by', is a fundamental Old English adverb and preposition meaning "near" or "alongside". The compound's literal meaning, "one who passes near," directly and logically describes its modern definition: a person who happens to be walking past a particular location. This formation exemplifies how English readily creates descriptive agent nouns by combining a verb with an adverbial particle to specify the circumstance of the action.

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', indicating a person who performs the action. - by: From Old English 'bī', meaning "near, at, during". In this compound, it functions as an adverb indicating proximity or location.