Anglish Phrase for "Alternate History"

I've heard "lore" and "yonderlore" for history, so otherlore? Would there be a more appropriate term? The timeline where William the Conqueror never invaded England is an [???]

Unrelated, but I thought "other" came from Latin due to the Spanish "otro", but it turns out "otro" is related to the Latin "alter" while "other" is Germanic. Neat.