What the word names now
Unfavourable is the ordinary English adjective for anything that works against a person, a plan, or a hope. Reviews, winds, harvests, first impressions, and medical outlooks can all be unfavourable. The British spelling keeps the ou of favour; American English writes unfavorable. The two forms are one word, not two histories.
The origin of the word unfavourable is a hybrid. English did not inherit it from Old English, and it did not import a ready-made negative from French. Speakers waited until the positive adjective was at home, then attached the oldest native negative prefix in the language.
A Germanic prefix on a Romance stem
The first piece is un-. Old English used it freely, and it remains the default way to reverse an adjective. It comes through Proto-Germanic un- from the same Indo-European negative n̥- that yields Latin in- and Greek a-. English could have formed something like infavorable on the Latin pattern, or followed French défavorable. It did neither. The home prefix was glued to a borrowed stem, as it later was in unnatural and unjust.
The second piece is favourable, recorded in English from the late fourteenth century. Middle English took it from Old French favorable, and that in turn from Latin favorabilis. Manuscripts of Gower, Langland, and Lydgate already show it, in spellings such as favourable, favorable, and faverable. Early senses were personal: well-disposed, kindly, even unduly partial. A chronicle could lean toward a pope; Fortune could lean toward the bold. Only in the mid-fifteenth century did the more impersonal sense “advantageous” become clear. Middle English also used the word for “attractive, pleasing,” a colour that has since faded.
The negated form is younger than the positive, and dictionaries do not agree on the first English date. Merriam-Webster, matching the historical citations behind the Oxford record, points to 1548, in Nicholas Udall’s Englishing of Erasmus on the Gospel of Luke. Other desk dictionaries place the adjective in the 1540s. A separate etymology dictionary, looking at the adverb, pushes the family back to the mid-fifteenth century, implied in unfavorably with the sense “with malicious intent.” The gap is real: the adverbial evidence is earlier and thinner; the adjective is securely in print by the mid-sixteenth century. Either way, English formed the negative on its own soil.
From Cicero’s noun to French favor
Latin favorabilis is built on favor, “good will, inclination, partiality.” Cicero is credited with coining that noun from the verb favere, “to show kindness, to be well disposed, to support.” The verb is older. It could describe a god leaning toward a people, a wind helping a voyage, or, in the ritual formula that asks the tongue to favere, the act of keeping speech free of ill-omened words.
What lies behind favere is disputed. One common proposal ties it to a Proto-Indo-European root reconstructed as ghow-e- or gʷʰew-, “to honor, revere, heed,” with a possible Germanic relative in Old Norse gá, “to heed,” and a Slavic one in forms meaning “to revere.” Other scholars prefer a root connected with “to be” or “to shine,” or they simply mark the Latin verb as uncertain. Michiel de Vaan, among others, has found the “worship, heed” link unconvincing. The Romance family is clear; the Indo-European parent is not.
The suffix -able is Latin -abilis as filtered through Old French. On the surface, then, the English adjective looks like un- plus favour plus -able. That analysis is only half historical. English favour itself is a thirteenth- to fourteenth-century loan of Old French favor, and the adjective was borrowed as a unit, not assembled in English from noun plus suffix in the first instance. Later speakers could reanalyse it that way, which is why favourable still feels transparent.
British ou reflects the French spelling tradition. American favor, favorable, and unfavorable were regularized toward the Latin vowel. The two standards are spelling variants, not separate roots.
How the negative filled its range
Once formed, the adjective followed the positive through its uses. It describes people and opinions that withhold approval; conditions and times that hinder; winds and weather that delay a voyage or a harvest; omens that bode ill. Those are not successive replacements so much as the same idea — not granted goodwill — applied to judges, climates, and stars.
The older personal colour of favourable, kindly or even biased, still shadows the negative. An unfavourable report is not merely inconvenient; it is a withholding of goodwill. In sixteenth- and seventeenth-century legal and moral prose the word can sit close to “regarded with disfavour.” Older Scots, borrowing the English form, used it of a defendant once guilt was proved. Modern English has thinned that personal charge. We now reach for the word as readily for a market, a prognosis, or a balance of trade as for a human judge.
Romance languages keep the same Latin stem but choose different negatives: French défavorable, Italian sfavorevole, Spanish desfavorable, Portuguese desfavorável, Romanian nefavorabil. Those are true cousins of the English stem. German ungünstig and Dutch ongunstig look like structural twins — a native un- or on- plus a “favour” adjective — but Gunst is a separate Germanic noun, not a descendant of Latin favor. The parallel is typological, not genealogical.
The join that still shows
The fact worth keeping is the join itself. English did not calque French défavorable, and it did not wait for a Latin infavorabilis. It waited until favourable was familiar, then applied a prefix already a thousand years old in the language. That is why the spelling can look French while the grammar feels English, and why the word still comes apart in the hand: not, favour, able to be granted.