before 900; Middle English, Old English than(ne) than, then, when, variant (in special senses) of thonne then; cognate with German dann then, denn than, Dutch dan then, than

Whether than is to be followed by the objective or subjective case of a pronoun is much discussed in usage guides. When, as a conjunction, than introduces a subordinate clause, the case of any pronouns following than is determined by their function in that clause: He is younger than I am. I like her better than I like him. When than is followed only by a pronoun or pronouns, with no verb expressed, the usual advice for determining the case is to form a clause mentally after than to see whether the pronoun would be a subject or an object. Thus, the sentences He was more upset than I and She gave him more sympathy than I are to be understood, respectively, as He was more upset than I was and She gave him more sympathy than I gave him. In the second sentence, the use of the objective case after than ( She gave him more sympathy than me ) would produce a different meaning ( She gave him more sympathy than she gave me ). This method of determining the case of pronouns after than is generally employed in formal speech and writing.
Than occurs as a preposition in the old and well-established construction than whom : a musician than whom none is more expressive. In informal, especially uneducated, speech and writing, than is usually treated as a preposition and followed by the objective case of the pronoun: He is younger than me. She plays better poker than him, but you play even better than her. See also but¹, different, me.