The 'knockers', or 'knackers' (Tommyknockers), are a special sort of underground spirit found in the mines.

The knockers used to be in general belief by the Cornish tinners, and were thought of as small, wizened, dried up little creatures, alleged by some to be the spirits of the Jews who had crucified Christ and who were placed in the mines to work out their doom.

The miner considered their presence lucky because they were scarcely seen or heard except in the neighborhood of rich lodes.

Knockers (pronounced knackers) are mine fairies, popularly supposed to be.the souls of the Jews who crucified Christ, sent by the Romans to work as slaves in the tin mines. In proof of this, they are said never to have been heard at work on Saturdays, nor other Jewish festivals. They are compelled to sing carols at Christmas time. Small pieces of smelted tin found in old smelting–works are known as"Jew's bowels." These fairies haunt none but the richest tin mines, and many are reputed to have been discovered by their singing and knocking underground; and miners think that when they hear them that it is a sign of good luck, because when following their noises they often chance on lodes of good ore. When a miner goes into an"old level" and sees a bright light, it is a sure sign that he will find tin there. Knockers like spriggans are very ugly beings, and, if you do not treat them in a friendly spirit, very vindictive."As stiff a Barker's knee" is a common saying in Cornwall; he having in some way angered the knockers, either by speaking of them disrespectfully or by not leaving (as was formerly the custom) a bit of his dinner on the ground for them (for good luck), they in revenge threw all their tools in his lap, which lamed him for the rest of his life. Mr. Bottrell tells a similar story of a man named Tom Trevarrow, who when he was working underground heard the knockers just before him, and roughly told them"to be quiet and go." Upon which, a shower of stones fell suddenly around him, and gave him a dreadful fright. He seems however to have quickly got over it, and soon after, when eating his dinner, a number of squeaking voices sang,

"Tom Trevorrow! Tom Trevorrow!
Leave some of thy 'fuggan' for bucca,
Or bad luck to thee to–morrow!"

But Tom took no notice and ate up every crumb, upon which the knockers changed their song to

"Tommy Trevorrow! Tommy Trevorrow!
We'll send thee bad luck to–morrow;
Thou old curmudgeon, to eat all thy fuggan,
And leave not a 'didjan' for bucca."

After this such persistent ill–luck followed him that he was obliged to leave the mine. [SeeTom Trevorrow for the story]

Bucca is the name of a spirit that in Cornwall it was once thought necessary to propitiate. Fishermen left a fish on the sands for bucca, and in harvest a piece of bread at lunch–time was thrown over the left shoulder, and a few drops of beer spilled on the ground for him, to insure good luck. Bucca, or bucca–boo, was, until very lately (and I expect in some places still is) the terror of children, who were often told"that if they did not stop he would come and carry them off." It was also the name of a ghost; but now–a–days to call a person a"great bucca" simply implies that you think him a fool. There were two buccas—

"'Bucca Gwidden,' the white, or good spirit,
Bucca Dhu, the black, malevolent one."