This term for a word newly coined in the hope it will become accepted may be thought a useful invention, one that’s particularly relevant to World Wide Words — coiners often submit linguistic inventions in the hope that they might be promoted and become a settled part of the language.
The difference between a protologism and a neologism is that the latter has actually been used somewhere, even if only once, while a protologism exists only as a suggestion of a word that might be used.
Wikipedia says that it was coined by Mikhail Epstein, then the Professor of Cultural Theory and Russian Literature at Emory University in the US but now Professor of Russian and Cultural Theory at Durham University in the UK. Wikipedia claims it was first used in 2005. Professor Epstein says of it:
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. ... Every newly coined word, even if it is deliberately promoted for general or commercial use, has initially been a protologism; none can skip that infancy phase.
The Transformative Humanities: A Manifesto, by Mikhail Epstein, 2012.
It’s from Greek protos, first, plus logos, word, but might equally be taken to be an blend of prototype and neologism.
As protologism is quite often used within the Wikipedia community, it is itself no longer a protologism, but has ascended to the status of a neologism and also that of jargon.