www.alphadictionary.com

Came across the word reading, and it just struck me - familiar as the word is - ‘immense’ is ‘not measurable’.
(IMmodest, comMENSurate)

Okay, I'm lost. I'm afraid I don't get what you're getting at here. Could you please elaborate?

What’s the mystery? I’m simply saying that ‘immense’ is one those words
we accept (well, I do, anyway) without ever wondering ‘whence?’
Once in a while, I have an interesting ideation of ‘thence!’

I’ve written similarly about ‘dilapidated’ and the relationship of ‘fashion’
to ‘fact’, ‘faction’, etc.

I was thinking too specifically of the word Bigly, not the general concept.

Hi. It’s one of the ways I love to twit ‘El Naranjo’ (the former President), but it’s really a word!

Most English speakers use big strictly as an adjective and a phrase in a big way for the adverb or use a synonym largely. I can't think of a reason off the top of my head. But the same restriction applies to its antonyms little and small. The odd man out is largely.

Thank you.
I should have been more thorough. The OED lists ‘bigly’ as an adjective - obsolete and of origin different from ‘big’.
Also as an adverb - rare - (< big adj. + -ly suffix), but with only
tenuously related meaning.