The word 'tautology' is a direct borrowing from Late Latin tautologia, which itself originates from the Greek tautología. This Greek term is a compound of tautó, a contraction of to auto meaning "the same," and -logía meaning "saying" or "speech." Thus, its literal construction is "the saying of the same thing." The concept entered English in the 16th century to describe a rhetorical redundancy, where the same idea is needlessly repeated. Over time, its application expanded into formal logic, where it denotes a proposition that is true in all possible interpretations due to its inherent logical structure, thereby preserving the core idea of "sameness" or repetition in a more abstract, technical sense.

Structure: taut (same) + logy (speech, discourse) taut: From Greek tauto, meaning "the same." It is a combining form derived from the phrase to auto ("the same"). logy: From Greek -logia, meaning "speaking," "discourse," or "study of." It is a suffix used to form nouns.