Which country used to be called Cathay?

Cathay is an alternative European historical name for China. During the early modern period, Europeans thought of Cathay as a completely separate and distinct culture from China. As knowledge of East Asia increased, Cathay came to be seen as the same nation as China and the term "Cathay" became a poetic name for the nation.

The name Cathay originates from the word "Khitan", the name of a nomadic people who founded the Liao dynasty which ruled much of today's Northern China from 916 to 1125, and who later migrated west after they were overthrown by the Jurchens to form the Qara Khitai. Originally, this name was the name applied by Central and Western Asians and Europeans to northern China; the name was also used in Marco Polo's book on his travels in China (he referred to southern China as Mangi). Odoric of Pordenone (d.1331) also writes about Cathay.

In about 1340 Francesco Balducci Pegolotti, a merchant from Florence, compiled the "Pratica della mercatura", a guide about trade in China, a country he called Cathay, noting the size of Khanbaliq (modern Beijing) and how merchants could exchange silver for Chinese paper money that could be used to buy luxury items such as silk. As European and Arab travelers started reaching the Mongol Empire, they described the Mongol-controlled Northern China as Cathay in a number of spelling variants.