M ost negative words have a corresponding positive word. So improbable is balanced by probable, and unreal is matched by real. Yet some negatives have no corresponding positives. Why can people be nonchalant but not chalant? How is it possible to be unruly but seldom or never ruly?

These are examples of the phenomenon known as unpaired negatives: negative words which seem to have no matching opposite. You may be gormless but can you ever have gorm? If ruthless people become merciful, can they be described as having ruth?

In fact many of these apparent unpaired negatives had a corresponding positive at some time. The word ruthless dates from the 14th century but the word ruth (meaning compassion) is found two centuries earlier.

People are sometimes described as hapless (unlucky), a word which dates from the 16th century. But earlier than this there really was a word hap (meaning fortune, especially good fortune) which clung on in English for several centuries, although it now sounds archaic.

The Oxford English Dictionary found the word unkempt used by Spenser in the 16th century but the word kempt existed from the 11th century (it originally meant combed').

The earliest example of unwieldy in the OED is from Chaucer's Canterbury Tales, about the year 1386, but he used wieldy slightly earlier in his Troilus & Criseyde to describe someone as vigorous or agile: "So fresh so young so wieldy seemed he."

Some of these positive forms, which existed earlier than the negatives but seemed to have died out, have been revived - often in a humorous context.

The word couth (the opposite of uncouth) appeared to have passed out of use but it reappeared in the late 19th century and seems to have established itself in the language again. In 1896, Max Beerbohm praised Walter Pater, referring to "The couth solemnity of his mind."

The Oxford English Dictionary lists the word disgruntled from 1682. You may not have thought there was an equivalent positive gruntled but the OED gives it as meaning "pleased, satisfied, contented", with its first example from P G Wodehouse's The Code of the Woosters (1938): "He spoke with a certain what-is-it in his voice, and I could see that, if not actually disgruntled, he was far from being gruntled."

It seems unlikely that there would be a word like domitable to provide the antidote to indomitable but the OED has actually found two examples - from 1677 and 1836. Similarly, the OED has peccable from 1604 to 1992, and shevelled from 1613 to 1886.

Several people have used the word ept as a deliberate antonym for inept. In a 1938 letter, E B White wrote: "I am much obliged . . . to you for your warm, courteous, and ept treatment of a rather weak, skinny subject." There are even examples of eptitude and eptly! The New Yorker for 11 March, 1967, got the former into a sentence along with two other unlikely positives: "The custom milliners are always full of ertia and eptitude - an attitude that I parage."

The word abled is a special case. It was used in the 16th and 17th centuries in the sense of capable or thriving, but it then died out until the late 20th century when it was revived to mean able-bodied (to contrast with disabled). Politically-correct speakers then began using it in combinations like differently-abled, to avoid using the word disabled, which might have been felt to have negative overtones.

In his book The Game of Words, Willard Espy published a poem crammed with what he called "forgotten positives": I dreamt of a corrigible, nocuous youth, Gainly, gruntled, and kempt; A mayed and a sidious fellow, forsooth - Ordinate, effable, shevelled, ept, couth; A delible fellow I dreamt.

Espy also pointed out that many words ending in -less have no matching positive word that ends in -ful. He wrote this poem to correct this "intolerable discrimination"

A tailful dog, one leaf-ful spring Set out for toothful foraging, And as he dug in rootful sod, Paid voiceful tribute to his God.

At which, a feckful, loveful lass, Whose strapful bodice charmed each pass- Erby, cried out, "O timeful sound!

O ageful, lifeful, peerful hound!"

Espy might have added many other such words, including backful, chinful, countful, gormful, limitful, motionful and spotful!

Tony Augarde is the author of The Oxford Guide to Word Games (OUP, £14.99) and The Oxford A to Z of Word Games (OUP, £4.99).