Good explanation about tsipouro, tsikoudia, raki, zivania, souma and
Apparently 'ouzo' which has come to replace 'tsipouro' is derived
from an Italian word stamped on export crates - 'uso Massalia'.
At the end of the article click on 'Cretan fire water: a personal
account'. It explains that grape pomace from wine-making is fermented
(I understand, with the addition of an equal weight of water) for
another month. In Crete they flavor their raki/tsikoudia with thyme.
The lengthy fermentation of grape pomace would certainly create lots
of congeners - hence its notorious reputation.
A good explanation about the related Turkish raki at: