You said it's not a thing. It is, in fact, a thing. I've heard it and said it often enough to be sure it's not so uncommon that it's reasonable to say it's not a thing.
You also need to keep in mind what Google Ngram is.
>> "When you enter phrases into the Google Books Ngram Viewer, it displays a graph showing how those phrases have occurred in a corpus of books (e.g., "British English", "English Fiction", "French") over the selected years."
It's a collection of books. Books remain relevant, but it tells you nothing of usage outside that. You only have to run a search on Google to see that it's used in a wide range of unrelated contexts. It's not some obscure anachronism or regionalism.
Much like how irregardless is now considered a thing. One of these days "mute point" will be a thing too :). I better not look that up, maybe it already is. I often wonder what people think they're saying when they misuse phrases like that.
Grow weary (tired of) and grow wary (suspicious of/concerned about) are different things though. Irregardless is a modification of the already useful regardless. I'm not sure how they're comparable.
That sure looks like a phrase used across a wide range of contexts and unconnected fields, too wide to support any notion that it's obscure. There's even a non-English news outlet using it in its English coverage.
You also need to keep in mind what Google Ngram is.
https://books.google.com/ngrams/info
>> "When you enter phrases into the Google Books Ngram Viewer, it displays a graph showing how those phrases have occurred in a corpus of books (e.g., "British English", "English Fiction", "French") over the selected years."
It's a collection of books. Books remain relevant, but it tells you nothing of usage outside that. You only have to run a search on Google to see that it's used in a wide range of unrelated contexts. It's not some obscure anachronism or regionalism.