Protologism is a term invented in the early 2000s by Mikhail Epstein, an American literary theorist, to refer to a new word which has not gained wide acceptance in the language. The word protologism describes one stage in the development of neologisms, at which a word is proposed, extremely new, or not established outside a very limited group of people. A protologism is coined to fill a gap in the language, with the hope of it becoming an accepted word. The term protologism is autological; it is an example of the thing it describes. Epstein coined the term by combining the Greek words and logos:
I suggest calling such brand new words 'protologisms' (from Greek protos, meaning 'first, original' and Greek logos, meaning 'word'; cf. prototype, protoplasm). The protologism is a freshly minted word not yet widely accepted. It is a verbal prototype, which may eventually be adopted for public service or remain a whim of linguo-poetic imagination.
According to Epstein, every word in use started out as a protologism, subsequently became a neologism, and then gradually grew to be part of the language. There is no fixed rule determining when a protologism becomes a stable neologism. According to Kerry Maxwell, author of Brave New Words:
[A] protologism is unlikely to make the leap to neologism status unless society connects with the word or identifies a genuine need for it [...] there's no guarantee that simple exposure to these creations will be effective in getting them used, as discovered by British inventor Sir James Dyson when he fruitlessly attempted to promote a verb dyson (by analogy with hoover) in the early 2000s.