de haut en bas is from the French, meaning high to low... rather than just top to bottom, it implies a sort of condescension: if you talk to someone de haut en bas, you're addressing them like an aristocrat talking to a servant, or maybe a teacher to a pupil.
Just what Rafarrin thinks, jno, when he talks about the people "d'en bas" and those "d'en haut" - it did nothing for his popularity except 'en haut' - and they say it's a classless society!