|Illustration from 'Roughing It' by Mark Twain|
Noun & adjective. Originally two words. Early 16th century.
[from BLACK adjective + GUARD noun: original significance unknown.]
I A body of people.
1. A guard or group of attendants black in person, dress or character. Obsolete. E16-18
2. the blackguard
2a. The lowest menials of a household; the scullions; an army's camp-followers. Obsolete. M16-E18
2b. Vagabonds, criminals, or vagrant children, as a group or class. L17-M18
II An individual.
3. obsolete. A guard or attendant black in person, dress, or character. M16-M18
4. obsolete. A vagrant child, a shoeblack, etc. Only in 18
5. A scoundrel, a villain; a foul-mouthed person. M18
6. More fully Irish blackguard. A kind of snuff. L18-L19
1. obsolete. Of the vagrant children, shoeblacks, etc. L17-L19
2. Scoundrelly, villainous; scurrilous. L18
blackguardism noun blackguardly language or behaviour L18
blackguardly (a) adverb (rare) in the manner of a blackguard; (b) adjective characteristic of a blackguard, scoundrelly, scurrilous. E19
Blackguard is one of the most treasured epithets in the English language, not only for its singularly idiomatic pronunciation (which is either as blaggard or blagg-ud) but also because it's just so much fun to use:
Percival! Thou art a fiend and a blackguard! Return my pen at once lest hot coals fall upon thine blackguardly head.
That's not a real Shakespearean quote, just in case you're wondering, but rather one I made up (and no, that's not the way youths on the street argue in Oxford). Mark Twain uses blackguard, however, in his semi-autobiographical novel Roughing It when describing a fearsome-sounding 'Destroying Angel':
"Destroying Angels," as I understand it, are Latter-Day Saints who are set apart by the Church to conduct permanent disappearances of obnoxious citizens. I had heard a deal about these Mormon Destroying Angels and the dark and bloody deeds they had done, and when I entered this one's house I had my shudder all ready. But alas for all our romances, he was nothing but a loud, profane, offensive, old blackguard! He was murderous enough, possibly, to fill the bill of a Destroyer, but would you have any kind of an Angel devoid of dignity? Could you abide an Angel in an unclean shirt and no suspenders? Could you respect an Angel with a horse-laugh and a swagger like a buccaneer?
And if you're wondering what the significance of a black guard is, the OED says that the original significance is unknown, although some theories have been put forward. One of these, as described in the definition, is that an army's most menial servants were collectively The Blackguard. These were the ununiformed caterers, servants and labourers that would have been in stark contrast to the higher ranks of attendants - without doubt a blackguardly crew.
Now be gone, thou blackguard, back to thine blackguardly deeds!
(although feel free to leave a comment if you like)