Having been living and working in the US almost all year, I have virtually recovered from mixing up British and American spellings. The only thing I sometimes still stumble over is a language quirk which I have fruitlessly searched for information about on Language Log. Hence this bleg.
There are a number of English verbs which are sometimes ended in the past tense with a t instead of ed: Dreamed/Dreamt, Burned/Burnt, Leaped/Leapt, Creeped/Crept, Learned/Learnt.
However, at least some of these are considered misspellings on this side of the pond, whereas other are not. Is there any rule on this, and, does anyone know where this variant in some past tense English verbs comes from in the first place? I wonder also if English ever used the words sweeped, weeped and sleeped before the current norms of swept, wept and slept.
Any information appreciated.