Most words ending in unstressed -our in the United Kingdom (e.g. colour, flavour, honour) end in -or in the U.S. (e.g. color, flavor, honor). Most words of this category derive from Latin non-agent nouns having nominative -or; the first such borrowings into English were from early Old French and the ending was -or or -ur.[1] After the Norman Conquest, the termination became -our in Anglo-French in an attempt to represent the Old French pronunciation of words ending in -or.[2] The -our ending was not only retained in English borrowings from Anglo-French, but also applied to earlier French borrowings.[3] After the Renaissance, some such borrowings from Latin were taken up with their original -or termination; many words once ending in -our (for example, chancellour and governour) now end in -or everywhere. Many words of the -our/-or group do not have a Latin counterpart; for example, armo(u)r, behavio(u)r, harbo(u)r, neighbo(u)r; also arbo(u)r in sense "shelter"; senses "tree" and "tool" are always arbor, a false cognate of the other word. Some 16th and early 17th century British scholars indeed insisted that -or be used for words of Latin origin and -our for French loans; but in many cases the etymology was not completely clear, and therefore some scholars advocated -or only and others -our only.[4]
As early as 1755 Dr Johnson settled on -our, while Webster's 1828 dictionary featured only -or and is generally given much of the credit for the adoption of this form in the U.S. By contrast, Johnson, unlike Webster, was not an advocate of spelling reform and for the most part simply recorded what he found. For example, documents from the Old Bailey, the foremost court in London, support the view of the OED that by the 17th century "colour" was the settled spelling. Those English speakers who began to move across the Atlantic would have taken these habits with them and H. L. Mencken makes the point that, "honor appears in the Declaration of Independence, but it seems to have got there rather by accident than by design. In Jefferson’s original draft it is spelled honour. " Examples such as color, flavor, behavior, harbor, or neighbor scarcely appear in the Old Bailey's court records from the 17th and 18th century, whereas examples of their -our counterparts are generally numbered in hundreds. One notable exception is honor: honor and honour were equally frequent down to the 17th century,[5] and Honor still is, in the UK, the normal spelling for a person's name.
In derivatives and inflected forms of the -our/or words, in British usage the u is kept before English suffixes that are freely attachable to English words (neighbourhood, humourless, savoury) and suffixes of Greek or Latin origin that have been naturalised (favourite, honourable, behaviourism); before Latin suffixes that are not freely attachable to English words,
In American usage, derivatives and inflected forms are built by simply adding the suffix in all environments (favorite, savory, etc.) since the u is absent to begin with.
American usage most often retains the u in the word glamour, which comes from Scots, not Latin or French; saviour is a common variant of savior in the U.S.; the name of the herb savory is thus spelled everywhere (although the probably related adjective savo(u)ry does have a u in the UK). The British spelling is very common for "honour" (and "favour") on wedding invitations in the United States.[7]
Commonwealth countries normally follow British usage. In Canada -or endings are not uncommon, particularly in the Prairie Provinces, though they are rarer in Eastern Canada.[8] In Australia, -or terminations enjoyed some use in the 19th century, and now are sporadically found in some regions,[9] usually in local and regional newspapers, though -our is almost universal.
Note to self: why does British spelling have humorist but colourist?