Interesting, it seems I learned/am using a modern American mutated version of the word.

https://www.broadlearners.com/t/understanding-the-meaning-of...

https://www.merriam-webster.com/grammar/whole-nother

https://old.reddit.com/r/etymology/comments/13s19j0/wtf_happ...

In my case, I was using it as almost a blend of the two meanings, something mostly meaning “unimpressed”, with a touch of “and a bit perplexed why such effort is going into this”. Basically a shoulder shrug and “okay…?”

I now find myself nonplussed, wondering if I should be using the word at all given it seems to have two opposite meanings.