The word is a straightforward Modern English compound adjective, transparently built from its constituent parts. The first element, "thin," descends from the Proto-Germanic thunnuz, which carries the core idea of lack of density or breadth. The second element, "face," entered English via French from the Latin faciēs, a term that originally denoted "form" or "appearance" before specializing for the front of the head. The suffix "-ed" is a productive adjectival marker in English, attaching to nouns to indicate possession of a quality. Thus, "thin-faced" logically describes one who possesses or is characterized by a face that is slender or lean in appearance, a direct compositional meaning that has remained stable since its formation.

Structure: thin (slender) + face (front of head) + ed (adjective suffix) - thin: From Old English þynne, meaning "not thick, slender, sparse." It functions as the primary descriptive adjective in the compound. - face: From Old French face, ultimately from Latin faciēs ("form, appearance, face"). It functions as the noun being modified. - ed: A Middle English suffix from Old English -ede, used to form adjectives from nouns, meaning "having, provided with."