You awoke one day in a place you didn't recognize, having no idea how you got there…and no memory of your own past.
This seems like a pretty common thing in worlds where there is magic, and inspired by the short-lived John Doe (which was on the same channel, season, and night as Firefly).
This background gives the option of letting the unknown past (aka, d20 rolls) determine things like skill, tool, and language proficiencies. A bit challenging to start out with, and it makes optimizing/synergizing a character's stats less likely, but could make for a fun character to play.