nimeämissä
Nimeämissä is not a widely recognized standalone term in standard Finnish. In Finnish grammar, the act of naming is expressed by the noun nimeäminen, and the standard inessive plural form for discussions about multiple naming events is nimeämisissä, meaning “in the naming processes.” The form nimeämissä is not considered a standard inflection and is typically viewed as a misspelling, typographical error, or a nonstandard/colloquial variant rather than a fixed grammatical form.
In practice, writers who intend to refer to multiple instances of naming would generally use nimeämisissä.
Usage considerations: when encountering nimeämissä in a text, editors should check for a possible intended form
See also: nimeäminen, onomastiikka (onomastics), nomenclature.