A lot vs. Alot: 9 Grammatical Pitfalls
1780, "mud, muddy land," from Irish slab "mud, mire dirt," itself probably borrowed from English slab "muddy place" (c.1600), from a Scandinavian source (cf. Icelandic slabb "sludge"). The meaning "untidy person" is first recorded 1887, from earlier expressions such as slob of a man (1861).
A miscalculation; an accident; glitch: There must have been a hell of a slip-up somewhere along the line (1874+)