Two lives under one spelling
English speakers use well to praise a performance, to report good health, to stall for a second in conversation, and to name a shaft of water. Those jobs sit in one dictionary spelling, but they are not one history. The origin of the word well is a pair of native inheritances that have travelled together since Old English and never needed a new form to keep them apart.
The first is the adverb of manner and degree: she speaks well, the meat is well cooked, it may well be true. From that adverb English later grew an adjective of fortune and health, and it already had, in Old English, an interjection of surprise or preface. The second is a water word: a spring or dug shaft, and a verb meaning to rise or gush, as tears well up. Treat them as neighbours, not as a single versatile root.
The adverb that meant as wished
The manner word is inherited, not borrowed. Old English wel already covered a wide field: abundantly, very, indeed, with good reason, nearly, and in a satisfactory way. Middle English kept wel, later written well. The same Germanic stock shows up as Dutch wel, German wohl, Old Norse vel, Old Saxon wela, Old High German wela, and Gothic waila.
Behind those forms linguists reconstruct Proto-Germanic wela or wala, understood as something like as wished or as desired. The deeper root is Proto-Indo-European welh₁-, a family of wishing and choosing. English will and weal belong here, as do Latin velle to wish and Welsh gwell better. Old English wela, well-being or riches, is the same desire seen from the side of having what one wants. A task done well was, in that older light, a task done according to wish.
English still marks the adverb of good with this word, but it does not form weller and wellest in ordinary speech. The comparative and superlative are better and best, an irregular set that matches a widespread pattern in words for goodness, comparable to Latin bonus, melior, optimus. That split is inherited grammar, not a later repair.
Health, filler, and extra force
Old English already used the adverb as an interjection and as a note of surprise. That is why modern well can open a turn in talk without describing manner at all: a discourse marker rather than a report of quality. By the middle of the twelfth century it could simply intensify a clause, as in may well be. Late in the same century it is recorded for a sound bodily state.
The adjective, from about 1200, first meant fortunate, glad, or blessed. Satisfactory is in place by the late fourteenth century; agreeable to wish or desire by the mid fifteenth; not ailing by the 1550s. In the health sense it is usually predicative: he is well. Attributive uses exist, but they are limited, as in a handful of medical compounds such as well-baby.
Middle English also locked in phrases that still feel idiomatic rather than compositional. Might as well and as well as are both attested by the late fourteenth century. None of this required a loan from French or Latin. The adverb simply kept adding jobs.
Scots weel and related northern forms show the same native line with a different vowel. They are dialect descendants, not a separate etymology.
Water that boils and rolls
The noun and the verb come from another Germanic verb of motion and heat. Old English weallan was a strong verb meaning to boil or bubble up, used of a river rising. Its causative, West Saxon wiellan and Anglian wællan, meant to make liquid surge. Middle English merged those intransitive and transitive lines into wellen, the source of modern to well.
Germanic relatives keep the bubbling picture in view: German wallen to seethe, Old Norse vella, Old Frisian walla, Old High German wallan, Gothic wulan to bubble or boil. Reconstructions of the Proto-Germanic verb vary slightly in shape (wallaną, wallijaną, wellanan), but they name the same rolling, boiling cluster. English wall is a related descendant, not a coincidence of spelling.
The usual Indo-European reconstruction is a root wel- or welH- meaning to turn or roll, with the water sense taken from roiling rather than from stillness. The Dutch specialist Dirk Boutkan has pointed out that the semantic step from turn to gush is not obvious. That caution is worth keeping. What is secure is the Germanic evidence for heat and surge, not a tidy picture of spinning water.
From the verb came the noun. West Saxon wielle and Anglian welle named a spring or fountain. The figurative sense, an abundant source from which something is drawn, is already Old English. A hole sunk for water is a later practical overlay: once a spring is used as supply, it is rebuilt as a shaft. English then stretched the same shape to the casing around a ship’s pump in the 1610s, a vertical opening through floors for stairs by 1700, and compact holders such as an inkwell by 1841.
German Welle wave and older forms meaning a spring sit on this side of the family. Distant kin of the rolling root, if the reconstruction is accepted, include Latin volvere to turn and English revolve. Those words do not belong with the adverb of wishing.
A pun the history does not share
Both inheritances were short native words. Both passed through Middle English with similar vowels. English never split the spelling, so a wishing well looks like a single idea: good fortune poured from water. Etymology does not support that blend. The pit belongs to boiling and gushing. The blessing belongs to will and weal.
A compact test is the Latin pair. Velle sits with the adverb. Volvere sits with the water verb. Mixing them is folklore. Keeping them apart is the record.
The dating worth carrying away is early and double. Before the Norman Conquest, speakers already had wel for manner, intensity, and exclamation, and they already named springs with wielle. Health as an adjective, the stair shaft, and the inkwell are later English jobs loaded onto two old Germanic words that happen, now, to look like one.