Though born in NYC, W. Clark Russell (1844-1911) was a very popular and respected English writer of sea stories. His father, Henry Russell, was the composer of the parlor song, "A LIfe on the Ocean Wave." The younger Russell was born in NYC, but both parents were English and he sailed on British ships, making his first voyage as a midshipman in 1857. He left the sea in 1865.

So I believe him when he says he can't recall hearing the word "chanty/shanty" used at sea. Remember that except for Nordhoff's (American) testimony from the 1840s, the word doesn't appear in print till 1868, after Russell had swallowed the anchor. As Nordhoff connects the word with the cotton-stowers of New Orleans, it may not have become generally applied to shipboard songs, even in the Gulf and the Caribbean, till during or just after the Civil War. Russell's observation should be taken seriously.

Neither Whall nor Robinson, who served at sea in Russell's time, insist that they'd heard the songs actually *called* shanties by the mid '60s. Even if they had, that doesn't mean that the word was universally known, as it apparently was by the '70s. (Without the broadcast media, new words didn't become entrenched as quickly then as now; even Davis & Tozier in 1888 thought they needed to put the word in quotes.)

When Russell wrote "in the forecastle," he meant, like many writers, "among deckhands," and not literally in the forecastle.

Russell's opinion that shantying arose in American ships looks more and more likely all the time.