What speakers mean now
Call two things different and the claim is usually modest: they are not the same. The adjective covers unlikeness in kind, quality, amount, or identity. It also marks things as distinct rather than interchangeable, and it can mean various or assorted, as when someone lists different reasons for the same choice. In casual talk it can go a step further and mean unusual, a polite or slightly ironic way of saying that something stands apart from what people expect. That last use is modern. The older core, unlikeness, has been part of English since the late Middle Ages.
A late medieval loan
The origin of the word different is a borrowing, not a native Germanic inheritance. It is first recorded in Middle English in the late fourteenth century. The Oxford English Dictionary’s earliest evidence is from around 1384, in the Early Version of the Wycliffite Bible. Standard etymologies take the English form from Old French different, and that French adjective from Latin differentem, the accusative of differens, the present participle of the verb differre (dictionary form differo).
The OED describes the English adjective as having more than one immediate source: partly French, partly Latin. Other dictionaries simply send it through Old French. The two pictures can sit together. Late medieval English took in many learned adjectives both from French speech and from Latin writing, and a transparent participle such as differens could have arrived by either route, or by both at once.
English already had a word for the same idea. Old English ungelic, built from un- plus gelic (like, similar), meant unlike or dissimilar. That native adjective did not disappear. Through Middle English unlic and unlich it continues as modern unlike, with close cousins in Dutch ongelijk, German ungleich, and the Scandinavian forms related to Old Norse ulikr. What changed is frequency. The Latin-French loan became the ordinary everyday choice; the older Germanic word stayed, but in a narrower role.
Carried apart
The Latin verb is a compound, and the compound is still readable in the English spelling. The prefix is dis-, apart or asunder. Before a following f it assimilates to dif-, which is why the word begins with a double f rather than disf-. The second piece is ferre, to bear or to carry. Put together they give a physical picture: to carry things in separate directions, to scatter, to set apart.
That prefix goes back to a Proto-Indo-European form reconstructed as dis-, a secondary shape connected with splitting in two and related to the root behind Latin duo and bis. The verb ferre continues Proto-Indo-European bher-, to carry. The same root is native in English as the verb bear. It also appears as Sanskrit bharati (he carries), Greek pherein (to carry), Gothic bairan, and Old English beran. Latin ferre supplied English with a whole cluster of later loans built on the same carrying verb: confer, prefer, refer, transfer, suffer. From the same participle family come difference, differentiate, and indifferent.
The ending -ent is the English spelling of the Latin present-participle suffix. In origin, then, different is the thing that is differing: the thing being carried apart.
Romance languages keep close relatives: French différent, Spanish and Portuguese diferente, Italian differente, Catalan diferent. German has borrowed different as a learned adjective, but the everyday native words are verschieden and unterschiedlich, built on a different root. Those are parallels in meaning, not descendants of differre.
How the senses sorted themselves
Classical Latin differre did more than one job. Transitively it could mean to scatter or separate. Figuratively it could mean to put off, postpone, or delay. Intransitively, especially in later prose, it meant to be unlike. English inherited that split and eventually wrote it as two verbs.
Differ, recorded from the late fourteenth century like the adjective, kept the sense be unlike and, from the sixteenth century, disagree. Defer in the sense postpone is historically the same Latin verb; spelling and stress were sorted out around 1500. A second English defer, meaning to yield to someone, comes from a different Latin compound, deferre (to carry down), and does not belong to this family. The adjective stayed with the unlike side. It never became a word for lateness.
The everyday English meaning has been stable: not the same. What grew around it is a set of constructions that style guides still argue over — different from, different than, and in British, Australian, and New Zealand English different to. Those prepositions are a later usage question, not a clue to the Latin compound. From is the form often recommended in formal writing because the related verb is differ from; than is well established in American prose, especially before a clause; to is common in some other varieties.
A genuine sense shift did arrive in the twentieth century. By 1912, sources record a colloquial use in which the adjective means special or out of the ordinary, often with a raised eyebrow: the new haircut is, well, different. The older Latin image of things carried apart is still there, but the comparison is now with what people expect, not with another named object.
The native leftover
One fact from this history is worth keeping on its own. Around 1384 a Bible translator could already use the learned participle in English. The older native word did not die; unlike is still available when a writer wants the Germanic shape of the same idea, and it still shows its kinship with like. The Latin one won the frequency contest, which is why a form that once named the act of being carried apart is now the ordinary way to say that two things are not the same.