1. (archaic) a slovenly or worthless person.
(This is a variant, but the whole passage is so fabulously insulting that I have to quote it. It’s also where I first heard the word years ago on this website....
The bun-sellers or cake-makers were in nothing inclinable to their request; but, which was worse, did injure them most outrageously, called them prattling gabblers, lickorous gluttons, freckled bittors, mangy rascals, shite-a-bed scoundrels, drunken roysters, sly knaves, drowsy loiterers, slapsauce fellows, slabberdegullion druggels, lubberly louts, cozening foxes, ruffian rogues, paltry customers, sycophant-varlets, drawlatch hoydens, flouting milksops, jeering companions, staring clowns, forlorn snakes, ninny lobcocks, scurvy sneaksbies, fondling fops, base loons, saucy coxcombs, idle lusks, scoffing braggarts, noddy meacocks, blockish grutnols, doddipol-joltheads, jobbernol goosecaps, foolish loggerheads, flutch calf-lollies, grouthead gnat-snappers, lob-dotterels, gaping changelings, codshead loobies, woodcock slangams, ninny-hammer flycatchers, noddypeak simpletons, turdy gut, shitten shepherds, and other suchlike defamatory epithets; saying further, that it was not for them to eat of these dainty cakes, but might very well content themselves with the coarse unranged bread, or to eat of the great brown household loaf. (Rabelais, Gargantua and Pantagruel translated by Thomas Urquhart in 1653)
1610s, from slubber "to daub, smear; behave carelessly or negligently" (1520s), probably from Dutch or Low German (cf. slobber (v.)). Second element appears to be an attempt to imitate French; or perhaps it is French, related to Old French goalon "a sloven." Century Dictionary speculates the -de- means "insignificant" or else is from hobbledehoy. (Online Etymology Dictionary, © 2010 Douglas Harper)
C17: from slubber (chiefly dialect variant of slobber) + invented ending (Collins Dictionary)