Thanks for tracking down the reference, Q.

This can't be proven, but if we had a time machine I'd be willing to make a wager that Colcord made up/spruced up that line. Am I impossible to please? No. But like most of Colcord's chanties, that one is a fairly transparent composite of elements from Whall's and Cecil Sharp's collections. As for that line, the part of "Missouri she's a mighty river" is there in Whall and, all things considered, it fairly marks his version. However, Whall pairs it with a non-rhyming phrase about the "redskin camp." Colcord was not going for the "redskin" theme, nor, it seems, would she tolerate a couplet that didn't rhyme! So she crafted a plausible-sounding second-phrase. My theory.

As for nonsense—just because Colcord couldn't understand it doesn't make it nonsense. Is poetry "nonsense"? I'm unclear. Poetry is a different "modality" (I dunno, I just chose that word - what's a better one?) of expression from prose, conversation, signage, etc. The modality of chanties is something that I think a lot of authors could not grasp, or else they needed to apologize for printing, so they called it "nonsense." I've noticed that a sort of trope of saying chanties were "nonsense" developed in the literature; it was well established by Colcord's time. Some people outright said chanties were trash because of it, though most, already endeared to the genre, apologized for it. They said that the words were just to create rhythm for work (ostensibly the most important thing) or that they gave vent to their predicament, etc—any way to avoid accepting the lyrics for themselves, to avoid dealing with them as potentially aesthetically satisfactory to someone.