Johnson derives this cant term, as he calls it, from black and guard, without attempting to explain their combination. Cant-words, above all others, have their origin in some strong figure of speech, or striking metaphor, and I believe the etymology of this is accidentally given by that strangest of all strange writers Stanihurst, in his explanation of an analogeous word among his own countrymen. "Kerne, he says, signifieth (as noble men. of deep judgement informed me) a shower of hell, because they are taken for no better than for rakehells, or the devil's black guard, by reason of the stinking stir they keep, wheresoever they be."
Holinshed, vol. 6, p. 68.
As Chaucer has been called the well of English undefiled, so might Stanihurst be denominated the common sewer of the language. He is, however, a very entertaining, and to a philologist, a very instructive writer. His version of the