The word 'stranger' originates from the Old French 'estrangier', meaning "foreigner, outsider". This, in turn, derives from the Latin adjective 'extraneus', meaning "external, foreign, from the outside", which is formed from 'extra' (outside). The core semantic journey is from the literal concept of "being from outside" to the more abstract sense of "being unfamiliar". The English agent suffix '-er' was added to the adjective 'strange' to concretely denote "a person who is foreign or unfamiliar". Thus, the modern meaning logically connects the ancient root for "external" to the contemporary idea of an unknown person or a newcomer to a place.

Structure: strange (foreign, unfamiliar) + er (agent suffix) strange: From Old French 'estrange', meaning "foreign, alien, external", from Latin 'extraneus' meaning "external, foreign". Functions as the core adjective meaning "unfamiliar". er: From Old English '-ere', an agent suffix indicating "one who is associated with or does something". Functions as a noun-forming suffix meaning "a person who is...".