The expression Liverpool pantile denotes a very hard ship’s biscuit.

This expression:
– refers to the fact that these sea-biscuits were particularly carried by Liverpool * merchant ships;
– likens the shape and hardness of these sea-biscuits to those of pantiles, i.e. roofing tiles curved to an ogee shape.

* Liverpool is a city and seaport, historically situated in Lancashire, a county of north-western England, on the Irish Sea.

The noun pantile was used of other flat cakes or biscuits—according to The Slang Dictionary; or, The Vulgar Words, Street Phrases, and “Fast” Expressions of High and Low Society. Many with Their Etymology, and a Few with Their History Traced (London: John Camden Hotten, 1864):

Pantile also means a flat cake with jam on it, given to boys at boarding-schools instead of pudding.

The noun pantile was used of any sea-biscuit—as indicated in Glossary of the Technical Terms used in the Evidence taken before the Royal Commission on Labour (London: Printed for Her Majesty’s Stationery Office, by Eyre and Spottiswoode, 1894):

Pantiles: Term used to express the hardness of old sea biscuits ground into meal and then re-baked.

In the sense of a sea-biscuit, pantile occurs in A Nautical Day, about life at sea aboard a merchant vessel, published in The Graphic. An Illustrated Weekly Newspaper (London, England) of Saturday 5^th June 1886:

The men wash and scrub away till about twenty minutes past seven. At this time a tinge of hope and pleasure asserts itself in their minds; the happy morning sleep of the watch below—their comrades off duty—is about to be destroyed. Somebody goes to the ship’s bell and strikes it seven times; it is “seven bells.” Immediately one of the scrubbing sailors runs with bare feet to the forecastle, as if he had just heard some beautiful melody, and was determined to follow it to its source. But what does he do? He does this: directly he enters the forecastle, he breaks into most abominable bathos. His sleeping comrades lie peacefully in their bunks around that unambrosial place. They slumber, they dream; they are enjoying the end of their four hours’ respite from the toils of life; yet this man enters like a vocal fiend of most violent discord to disturb them. He looks at them, and he yells, “Hi, you sleepers—seven bells, here—show a leg, come!” He continues in this strain till he has uttered enough noise to awaken a dormouse in the depth of winter. Then the watch below wake up, as is only natural; they stir in their bunks, relinquish their black blankets, and crawl out on to their sea-chests; thence to the deck. They do not trouble themselves with any trivialities of the toilet. Life is short, fresh water is precious, and personal appearance is a frivolity at sea. One of their number proceeds to the galley—the nautical kitchen—and receives from the cook a can of coffee; this together with sea-biscuits forms the sailor’s breakfast. The coffee is a black mystery stewed to distraction; the biscuit resembles an edible stone, tolerable as a curiosity, but monotonous as an article of daily diet. Yet weevils are a painstaking race of infinitesimal creatures; they love to live and die in this sea-biscuit. As a hard-hearted comestible it has no rival. A sailor takes one of the things from the “bread-barge,” and smites it against his knee; he repeats the process, but the biscuit is imperturbable; the man becomes interested, and crashes it against the corner of his sea-chest; at last the “pantile” breaks, and the mariner is able to breakfast. True, some of the biscuits are soft, but the weevils generally find out this before the man.

These are, in chronological order, the earliest occurrences of the expression Liverpool pantile that I have found:

1-: From a letter to the Editor, by ‘A Deteriorated Seaman’, published in The Daily Post (Liverpool, Lancashire, England) of Thursday 14^th April 1870:

I sailed from Liverpool in 1855 for a port which we never reached. We commenced to pump soon after leaving dock, and after being tired of that we received for refreshment what sailors call a Liverpool pantile and some stunsail-boom tea; next the raw coffee beans were sent into the forecastle, and afterwards we had to get them roasted how we could; and when we did, at breakfast time—after being eight hours through the night at the pumps—we went below. The worst of American beef and a pantile flanked by raw coffee, beans, and hot water ad libitum, was our fare to make us ready for another spell at the treadmill (called a brake). The forecastle leaked so much that we got the watch going on deck to cover us, when in our hammocks, with oilskins, and leave nothing bare but our mouths to breathe. It may be said bad weather was the cause of it; but it was not so. She was leaking when leaving the dock. They may say that that was an exceptional case; so is Captain Turner’s. But, if it is different now, what becomes of all the old ships that we hear of daily? As a well-known person remarked, a ship is a prison with a good chance of being drowned in it. If a man does not wish to risk that he runs the risk of three months on the treadmill, or imprisonment of some kind. Again, receiving half their wages in foreign ports, what do the sailors do with it? In Bombay, for instance, their jaws are so strained with crunching pantiles that they buy soft bread, and as regards the water-bewitched they even buy their own coffee and sugar.

2-: From a letter to the Editor, by ‘A Sailor’, published in the Belfast Evening Telegraph (Belfast, Antrim, Ireland) of Saturday 18^th February 1882:

As a rule, any person who has any connection with shipping thinks he has more right to Jack’s wages than himself. Shipowners screw them down to the last farthing. Sea captains, tailors, and sailors’ crimps—all combine, each in their own way, to make Jack’s wages as small as possible. The present wages of sailors is from £2 15s to £3 5s per month—£2 15s for the Southward and Atlantic trade, and £3 5s for coasting, the former being 1s 10d, and the latter 2s 2d per day, allowing 30 days to the month as they are sometimes paid, including food, of course, which consists of American beef and pork, very often of the worst description, pea soup, a mixture of flour and water, called duff; coloured water, called coffee; and ditto, called tea; hard Liverpool pantiles (known to shore people as sea biscuit), with about as much nourishment in them as you would get in a snowball; varied on Sundays by a fresh mess, the fresh mess consisting of a tin of preserved meat, thrown into a pot of boiling water, with a few potatoes or a handful of flour; in general the meat is skimmed off and taken aft to the cabin, the sailor’s share being the greasy water and hard-boiled lumps of flour, called by sailors dough-boys—in short, the whole lot would cost the owners about 1s per man per day.

3-: From Our Sailors, by ‘One who swallowed the anchor’, published in The Ayrshire Post (Ayr, Ayrshire, Scotland) of Friday 9^th April 1886:

We shall now see […] what is supposed to be breakfast on Monday morning. Jack gets coffee and the remains of Sunday’s salt beef, with the coarsest of coarse biscuit, ironically called “bread” in the shipping articles—Liverpool pan-tiles sailors call them, with about as much truth as the articles. But, and mark you, this is no uncommon occurrence on a long voyage, this bread in course of time, and despite the iron tanks it is kept in, begins to breed maggots, the inside being often eaten away, and filled up by a colony of these interesting insects. This is no exaggeration, but an actual truth. On one occasion I can vouch for, the crew of a Glasgow ship in a foreign port complained to the captain of their bread being in this condition, and what, think you, was done. The bread was sent ashore, the baker put it into the oven, roasted the maggots, and sent it back again, dead animal matter, which could only get worse as it got older. As a matter of course, the crew refused to put to sea until they got new bread. I need scarcely say that they got it.