Laccun
From The Stargate Omnipedia
Term from a very old dialect of the Ancients that translates as "lost." Using Daniel Jackson's erroneous notes, Jonas Quinn incorrectly translates the word as meaing "of the lost." He concluded that the Ancient term for the "Lost City" is actually the "City of the Lost" -- leading SG-1 to the planet Vis Uban
Daniel is forced to revise his previous theories when he returns from the Ancients with the ability to read the language.
KEY EPISODE
Fallen - Using Daniel Jackson's notes, Jonas translates "laccun" to be "of the lost" -- leading him to a theory that sends SG-1 to Vis Uban.