A small word with a large job
English speakers use full for almost any kind of completeness. A glass is full when it holds as much as it can. A report is full when nothing essential is left out. After a meal, a person is full in a more bodily sense: sated, with no room left for another helping. The same spelling also works as an adverb in older-flavored phrases such as full well, and as a noun in formulas like in full and to the full. Clothing can be full when it is cut with extra fabric. A moon is full when its whole face is lit. None of this range is recent fashion. The core adjective was already stretching across amount, quality, and satiety in Old English.
Native, not borrowed
The origin of the word full is inheritance, not a loan from French or Latin. Old English had full and the shorter spelling ful. Middle English kept both ful and full, with southern spellings such as vol in some manuscripts. Historical dictionaries place the earliest English use in the Old English period, before 1150, and treat the adjective as a Germanic inheritance rather than a medieval import.
That Germanic ancestor is reconstructed as *fullaz. It is the source of a tight family of lookalikes still easy to recognize: German voll, Dutch vol, West Frisian fol, Old Norse fullr, Swedish full, Danish fuld, and Gothic fulls. Scots fou, sometimes used for drunk, is a close relative of the same adjective. English has even taken that Scots form as a rare doublet, though only as a dialect or literary oddity. The map is the usual one for a native English word: West Germanic into Old English, then a continuous life through Middle English into the modern spelling.
From a past participle meaning filled
Behind *fullaz stands a still older Indo-European adjective, reconstructed as *pl̥h₁nós. Comparativists treat it as a past participle of a verb meaning to fill. Handbooks write that root in several notations—*pleh₁-, *pele-, pelə-1—but they are pointing at the same family, not offering rival histories. The Germanic double l is not decoration. An earlier cluster *ln assimilated, so a form along the lines of *pulnos became *fullaz. That sound change is why English has a short vowel plus ll rather than an n in the middle of the word.
The same participle, after different sound laws, produced Latin plenus, Welsh llawn, Lithuanian pilnas, Russian полный, Sanskrit pūrṇa, and Persian por. English therefore shares distant cousins in plenty, plenary, complete, replete, deplete, plus, and supply, all of which arrived later through Latin or French. The native adjective and the Romance loans describe overlapping ideas because they started from one root and then traveled different routes into the vocabulary.
The verb fill is not the parent of the adjective. Old English fyllan, from Germanic *fulljanan, is a derived verb: to make something full. Fulfil, from late Old English, began as a transparent compound meaning to fill something until it is full. The noun fill, and Old English fyllo or fyllu for fullness and satiety, belong to the same cluster. The adjective is the hub; the rest grew off it.
Completeness, satiety, and the moon
Old English already used the adjective for a container that would hold no more, for a person who had eaten or drunk enough, and for things that were perfect, entire, or utter. Those three strands are still alive. Informal full after dinner is not a joke derived from modern slang; it is one of the oldest recorded senses. Completeness of amount and completeness of quality sat side by side from the start, which is why a full account and a full cup still feel like the same word rather than two accidents of spelling.
The adverb is equally old. Old English ful meant very, fully, entirely. It was common in Middle English in combinations such as full well and full many, where it intensified the next word instead of describing a container. A tighter sense, quite or exactly, is dated to the 1580s. Surviving phrases keep the older intensifier even when speakers no longer feel it as a separate word standing beside the adjective.
The moon supplies a concrete picture of the same idea. Old English already had a genitive phrase for a full moon, a disc lit from edge to edge. Later English kept building compounds from the adjective: a theatrical full house is recorded from 1710; the poker hand of three of a kind plus a pair appears in the late nineteenth century, after an earlier full-hand. Full-dress, for clothing suitable to a formal occasion, is eighteenth-century. In Australian English, full can still mean drunk, a sense that matches Swedish full and other Scandinavian uses rather than a new invention from nowhere.
Some older literary senses have faded. Writers once called a person full when the mind was stocked with knowledge, or when attention and feeling were absorbed in a subject. Those uses sit close to modern full of, but they are no longer the default reading of the bare adjective. The core has stayed remarkably stable: holding as much as the situation allows, whether the thing in question is a vessel, a narrative, a legal power, or a stomach.
A lookalike from the workshop
English also has a verb full that means to beat or shrink cloth so that it becomes denser. That verb is a different word. It entered Middle English in the late fourteenth century from Old French fouler, to trample or press, from Latin fullo, a fuller or cloth-worker. Some accounts suggest the English verb may instead have been back-formed from Old English fullere, an agent noun already borrowed from that Latin trade name. The Latin noun itself is uncertain. One major etymological dictionary leaves it unexplained; another ties it to a separate Indo-European root connected with shining or white, perhaps from the look of cleaned cloth. Either way, the fuller in a mill and the everyday adjective only look related.
That accident is the useful reminder. The common adjective is native Germanic, built on an ancient participle meaning filled. The cloth verb is a Latin craft term that happened to land on the same three letters. Containers, meals, moons, and poker hands all ride the first word. The mill rides the second.