Hospitality in four parts of speech
Speakers of modern English treat welcome as several words that happen to share a form. It greets someone at the door. It describes a guest, a letter, or a change in the weather that arrives as a relief. It names the reception itself, friendly or chilly. It is also a verb: hosts welcome visitors, and a tired person might welcome silence. A later courtesy, you're welcome after thanks, sits on the same stem, as does the permission formula you are welcome to stay. All of these uses share one idea: an arrival, a gift, or a request is received with pleasure rather than resisted.
That range is old, but the spelling is a rewrite. The origin of the word welcome is English from the start. It was not borrowed from French bienvenu, even though the two greetings later grew to look like cousins.
A wished-for guest in Old English
In late Old English the core form was wilcuma, a masculine noun for a desirable guest: someone whose coming matched another person's will. The same material served as a greeting, wilcume, and as a verb, wilcumian, also written welcumian and wylcumian, to receive a person gladly. Standard dictionaries place the first English use before the twelfth century. The noun already appears in Old English poetry, including Beowulf, where arriving men are called welcome among the Danes.
The compound is inherited West Germanic, not a medieval import. Old High German had willicomo. Middle Dutch had both willecome and wellecome. English carried the word through Middle English in a scatter of spellings: wilcume, wulcume, wolcome, welcume, and at last welcome. The shift of the old short u toward o in the second syllable follows a wider Middle English spelling habit and does not mark a new source language.
Desire plus a comer
The first element is Old English willa, pleasure, desire, or choice, the same family as the noun will. Behind it lie Proto-Germanic wiljaną and a Proto-Indo-European root reconstructed as welh₁-, to wish or choose. The second element is cuma, a guest or comer, from the verb cuman, to come, from Proto-Germanic kwemaną and Proto-Indo-European gʷem-. Historical linguists reconstruct the whole as Proto-Germanic wiljakwemô, a wished-for arrival or guest.
Modern English conceals that cut. In Middle English the first half was drawn toward the adverb well. Once speakers stopped hearing cuma as a free noun meaning guest, the second half lined up with the ordinary verb come. Historical dictionaries also note pressure from Old French bien venu and Latin greeting formulas of the bene venisti type, which treat an arrival as something that went well. How much French actually moved the English form is not settled. The native adverb well is enough to explain most of the change, and a similar swap of wel- for wil- appears in Dutch welkom.
German willkommen still shows the older will- more plainly than English does. West Frisian wolkom, Danish and Norwegian velkommen, Swedish välkommen, and Icelandic velkominn belong to the same Germanic set. Scots has walcome. Old French itself borrowed a Germanic wilecome, so the Romance and Germanic greetings were already in contact. Whether the Scandinavian forms are independent coins or later alignments with Low German remains unclear.
Romance bienvenu, benvenuto, bienvenido and their relatives look like well plus come as well. They are not inherited from Classical Latin, which has no matching compound. Some accounts treat them as early calques from Germanic into spoken Latin. That is a parallel history, not a source for the English word.
From a kind of person to a kind of reception
The sense of a welcome as a type of person, the guest you wanted, is Old English and then fades. What stayed was the greeting, the adjective for an acceptable visitor, and the verb of receiving. By about 1200 the adjective could describe events and permissions, not only people in a doorway: a thing might be gladly allowed. Around 1300 it could mean agreeable or pleasing of a gift or a change. In the fifteenth century invitations begin to add and welcome, a way of saying that someone is freely permitted to take or do something, almost answering thanks before they are spoken.
By the 1520s the noun is recorded for a kindly greeting on arrival and for public entertainment offered as that greeting. Later still come set phrases built on the same base: the welcome mat in the first decade of the twentieth century, and the welcome wagon around 1940. Wear out one's welcome, stay until the pleasure wears off, is the old guest sense turned inside out. The word kept making social formulas long after its first half had been rewritten.
The fixed reply to thank you is newer in print than the rest of the family. Historical dictionaries often cite a 1907 example of you're quite welcome after thanks. Earlier nineteenth-century instances of you are welcome and you're quite welcome in that role do exist, and a line from Othello around 1603, your honour is most welcome after thanks, is sometimes offered as an ancestor. That Shakespearean line is still close to a greeting of a person, not yet the automatic two-word minimizer of modern courtesy. The thanks-reply almost certainly grew out of the older permission sense, you are welcome to it, compressed into a social formula that written English recorded late because such talk was rarely worth setting down.
The German form that kept the first half
Anyone who looks at welcome and hears well plus come is not inventing a wild folk story. That reading is the Middle English reanalysis the spelling now freezes. German willkommen still advertises the older first element, will, desire. That contrast is the fact the word leaves in plain sight: what looks like a wish that someone came well began as a name for the guest you wanted.