Sorry to be pedantic, but Step 1 is to see if anybody—anybody who used language authentically with respect to the issue—ever sang this. Step 2 is to determine exactly what they said, and Step 3 is the analysis and discussion :)

"The Wild Goose" provides no evidence that such a phrase was used. But Lloyd's creation from the fragment, which alludes to a lady's bouncy boobs, is so popular and well-known through his album and people's cover versions of it that the line might rattle around in our heads as something we imagine to be traditional pre-1950s.

Unfortunately I don't know Andrew Calhoun's album, just that that particular couplet doesn't ring authentic to me in the context of "Shenandoah." Too bad he doesn't say where he learned it from or how he constructed his rendition. That is the problem. Am I cynical enough to think that Lloyd's recording put "quiver" into the consciousness of late 20th century performers, and this manifested in Calhoun's rendition? Yes, I am.

The Williams article provides some authentic evidence. Williams was a biracial American sailor who's sea career started in the late 1870s and who served in countless ships. I think some of his comments *about* chanties in his articles are deluded at times (!), but there is no reason to think his line wasn't sung.

I did a search on my notes which have very many of the documented lyrics of chanties from most collections. The notes don't include the complete lyrics in Hugill, however, nor some of the other later collections (which generally don't offer much original anyway). The Williams piece was the only one where the word "quiver" turned up in the search.

Therefore, I'd only interpret the meaning of the phrase from the Williams "Blow Boys Blow."

However, it does seem likely that other people would have rhymed "river" and "quiver" at some point! Though "shiver" is a more plausible rhyme, I think. When we get some more examples, it may shed more light!