Below is Mary Cadwalader Jones, recalling a voyage taken with her father on a Union blockade ship between Charleston and Havana, April 1865, published in 1924 in Volume 59 of the literary journal The Bookman. Found on page 160 at Google Books, here.

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I think the crews liked the company of a young girl who was frankly interested in whatever they could show her, and I can honestly say I have never been in better mannered company. Sometimes when they were in the full swing of a chantey they would suddenly mumble a verse, or evidently jump it, if I came near, but I never heard a word which could shock the most Victorian propriety. One of the chanties, about Ronzo, was a favorite, for it had a lilting tune, and gave a chance for improvisation. It began:

Ronzo was a tailor,
Ronzo, boys, Ronzo,
But now he is a sailor,
Ronzo, boys, Ronzo,

and went on to take Ronzo “round the Horn, where we showed him many a storm”, and “round the Cape, where he with fear did shake”, and to every place to which a rhyme, good or bad, could possibly be tagged, ending in a fine full burst:

But now he is a sailor,
Ronzo, boys, Ronzo,
And not a damed old tailor,
Ronzo, boys, Ronzo.

(They tried to sing “darned” on my account, but they often forgot.)

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Google Books has provided a few other leads on “Ronzo” texts that I am tracking down in full.