English is a fascinating language, and like all languages has its fair share of interesting oddities. Unpaired words are one such oddity – they are words that would appear to have a related word or one with the opposite meaning, but don’t.
For example, the words disambiguate, inevitable and unkempt would seem like they have direct antonyms given the prefixes in- and un-, but the words ambiguated, evitable and kempt don’t exist.
Most unpaired words are a result of words falling out of use. However, many never had a ‘normal’ form in the first place, but happened to start with the same letters as common prefixes, such as dis-, in- and un-.
Some words have been retroactively formed, usually in for humorous purposes – gruntled as an opposite for disgruntled is one such back formation. Popular TV show writer Joss Whedon (best known for shows like Firefly, Buffy the Vampire Slayer and Dollhouse) is especially fond of using these in his dialogue.