I'm pretty sure it also preceded the great majority of those domains.
The other big one, 37signals, is named after the signals sent into space in search of intelligent life. No clue re: 43things. All the other numbers exist because every other url was taken.
I think the other 43 domains followed 43folders, they succeeded it by a year or three IIRC.
The other big one, 37signals, is named after the signals sent into space in search of intelligent life. No clue re: 43things. All the other numbers exist because every other url was taken.