[1] Silver used the term for fused words, or for phrasal words like "La Brea Tar Pits" as a proper noun.
[2] The term is also used by some Korean linguists to capture the common phenomena between grammaticalization and lexicalization, i.e., to capture the phenomena that result in new morphemes via reanalysis, fusion, coalescence, univerbation etc.[3][4][5]).
In addition to traditional examples of grammaticalization (for example, 'wanna' from 'want to' or 'gonna' from 'going to', etc.
A very clear reason that those lexemes are not analyzable into smaller pieces is that the sum of those pieces from any of the lexemes wouldn't equal to the original meaning.
Recently, the term 'morphemization' is also used to indicate morphologization in Chinese linguistics.