Neologism

Etymology

From French "néologisme", from Greek "neos" (new) and "logos" (word), formed in the 18th century when rapid coinage first seemed worth naming. It was often an insult — a charge of needless invention — before it settled into a neutral technical term.

noun · /nee-OL-uh-jiz-um/
A newly coined word or expression not yet in established use.
What it names
The living edge of a language — words on probation, before dictionaries decide whether to admit them.
Example
"Doomscrolling" was a neologism in 2019 and a dictionary entry within three years.
Related idea
A neologism is any new word; a portmanteau is one particular way to make one — fusing two existing words, as "smog" fuses "smoke" and "fog."