A shellback is a U.S. Navy term for a sailor who has crossed the equator. Until that ceremony, he is a pollywog.
Ewan MacColl wrote this song about his interviews with the sailor Ben Bright Charles Parker in London. From mudcatter Jim Carroll:
Then somewhere in his seventies, he had been under sail, jumped ship in the US in the 30s and worked with the I.W.W. (Wobblies), given songs to J. M. Carpenter, and had ended up in London acting as an assistant to a escape artist who performed for the tourists visiting The Tower of London. Parker and MacColl recorded him in his bed-sitter in North London until one day they turned up at his home to find he had joined the crew of a cargo vessel heading for Australia. He was last heard of working on a coaster in South Australia. MaColl and Seeger produced a monograph on his life and experiences, and MacColl wrote this based on his description of life at sea.
I am a bold sea-faring man, I come from everywhere;
Name any point of the compass you like, you're bound to find me there.
Born in a gale in the Roaring Forties, entered in the log -
Sent up aloft to the tipper t'gan's'ls, and christened in navy grog.
All that I own are the clothes on me back and the tools of the sailor's trade;
Me fid and me palm, a few needles, a spike, a knife with a good, keen blade.
I've a hunk in the fo'c'sle, a place on a bench in the galley where I can feed,
And a hook for to hang me old oilskins up. What more does a shellback need ?
Been up in the rigging with Lascars and Swedes when the stormy winds do blow;
Bunted the royals with Arabs and Finns with the boiling sea below;
Hauled on the braces with Friesians, damn near drowned in the same big wave;
Chinamen, Yankees and Scousers and all of 'em bloody hard men to shave.
I've sailed both Atlantics and doubled both Capes more times than I can tell;
Fought the big seas in a parish-rigged barque and froze at Cape Farewell.
I've cursed the calms in the Doldrums when you'd swear the wind was dead;
Laid to off the Horn in a westerly gale that would blow the hair off your head.
I've shipped in high-loaded East Indiamen, been crew on a coastal barge;
Come bowling along on a smart clipper ship when she was running large.
Schooners, lime-juicers and barcatines, they're all well-known to me,
And I've worked as a flying fish sailor dodging the reefs in the China Sea.
To the maggoty beef and weevily bread, I've added me word of abuse;
I've pounded hard biscuit to powder and mixed it with bug-fat and jaggery juice.
With the galley awash for a week on end, I've gore hungry early and late;
Been served with pea-soup that could stand on the poop deck and scare off a blue-nosed mate.
I've signed on in short-handed Yankee ships with masters who know the score;
I've sailed with the drinkers who can't navigate a course past the bar-room door.
I've been with masters who're seamen and know how to treat a sailor well,
And some of the others, the miserable buggers, have made me life a hell.
I know all the boarding-house keepers ashore from Cardiff to Tokyo;
Know all the crimps and waterfront pimps from Riga to Callao.
I've spent me advance at Rasmussen the Dane's, I've lodged with Paddy West,
And I've know the slop-chest to take half of me screw while Big Nellie she took the rest.
I've sailed out of Rio in ballast, I've loaded grain in Frisco bay;
Raced with a cargo of tea from Shanghai on the old Thermopylae;
I've carried nitrates from Iquiqui and whisky out of Leith;
Sailed in the woolrace on old Cutty Sark, with the wind between her teeth.
Goodbye, you square-riggers, your voyaging's done, farewell to the days of sail;
Goodbye, you Cape-Horners and every tall ship that ever defied a gale;
Goodbye to the shellbacks who rode the winds through a world of sea and sky,
Your roving is ended, your seafaring's over; you mariners all, goodbye.