"protologism" vs "neologism"

[Fimbriae]

As the subject demonstrates, my query here is to make sure of the slight difference between the term "protologism" and "neologism."

So, if anyone has any clues about them, let me know them, please.
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[Cerberus™]

A neologism is simply a newly invented word or saying. It comes from Greek neos, "new" or "young".

Protologism doesn't exist according to the Oxford English Dictionary. It probably comes from Greek protos, "first". Whoever invented this word perhaps needed a term for a word that has the same meaning a certain neologism, but that, as opposed to the neologism, has existed before.