Thule (pronounced thew’-lee or thoo’-lee, with th as in thank) is the ancient Greek and Latin name for the most northerly habitable place in the world, said to be six days’ sail north of Britain.
Although it was presumably named for a real place, there is considerable uncertainty as to just what place was that designated as Thule, and guesses range from Norway to Iceland.
The Thule in Greenland at which the United States has recently established an Air Force base is named in remembrance of this unknown land of the ancients and is pronounced too’-lee.
But Thule has also acquired a figurative meaning, which is “the extreme limit of travel,” and this has led to the phrase ultima Thule (“farthest Thule”), with the meaning of “the utmost attainable, the limit, ‘the most.'”