Who is Little Leroy the Cabin Boy?

Translating Harding's Tinkers to Hungarian I've stumbled upon this phrase too, and found several a beer-songs / limericks that could explain the conversation: Little Leroy could be the name of the cabin-boy mentioned in these songs who was cautious enough to "packed / lined his a** with broken glass" as to avoid being raped by his horny shipmates. (Though I couldn't find any of them where the cabin-boy's actually called little Leroy.) These poems / songs pictures (rather vulgar) life on a ship, from the story of Columbus to the North Atlantic Squadron's song and more.

As for those not being familiar with Harding's book, the conversation is between a freshly shaven old man and his grandson - the latter telling him that he looks pretty like Little Leroy the cabin-boy, and the grandfather answering that he was a "cautious little nipper" - this phrase is included in each of the above mentioned limericks.