It’s a search of Google books, but the question still stands, what the Fuck happened in 1870
I CAN ANSWER THIS!!
In the Cornish dialect of English, Pokemon meant ‘clumsy’ (pure coincidence).
In the mid 1800s there was a surge of writing about the Cornish language and dialect in an attempt to preserve them with glossaries and dictionaries being written. I wrote about it HERE.
EDIT: The original NGram is a fake! So this makes Pokemon an even weirder coincidence.