There's an old A Wyatt Mann cartoon with an incredibly racist (obviously, given the author) depiction of a black dude saying gibberish into his cell phone (the words "bix nood" being part of this gibberish), and it became a meme.

it's from some racist cartoon series, in this case they were doing a caricature of African-American Vernacular English

This is probably the least problematic page explaining this, but it's a series of white supremacist cartoons that became 4chan memes - huge CW racism, white supremacy, SA, antisemitism, and probably a dozen other things: https://knowyourmeme.com/memes/people/a-wyatt-mann

In short, it's from an extremely racist cartoon with a panel of a racist chariacture of a black person talking "gibberish".

https://en.wiktionary.org/wiki/bix_nood

From a comic by the cartoonist A. Wyatt Mann, which depicts a black man speaking in gibberish. It was later reuploaded by users of the 4chan image board /b/. It has no known discernible etymological root.

Not going to link the original comic since it's wildly racist. But the same guy who drew the happy merchant meme drew this cartoon depicting a black woman badly.