In Bhutan, Tartary is called 'Sopo'
Editorial contextIn a Portuguese letter of 1627 from the kingdom he calls Cambirasi (Bhutan), Estevao Cacella reports that the local king says the people of Sopo are more valiant than the Chinese and usually beat them, which Cacella links to the well known wars of the Tartars with China. He then explains why nobody there has heard of 'Cathay': local people use quite different names, calling China 'Guena', Tartary 'Sopo' and Tibet 'Potente'.
but that the [people] of Sopo are more valiant, and so this one commonly defeats the Chinese, all of which agrees with what is so well known of the war of the Tartars with the Chinese … for neither China nor Tartary nor Tibet is known by these names, of which they have no knowledge; and they call China Guena, Tartary Sopo and Tibet Potente
Working translation
Original wording
porem que a do Sopo he mais esforçada, e assi commummente esta vence os Chinas, o que tudo diz com o que he tão sabido da guerra dos Tartaros com as Chinas … pois nem a China nem a Tartarea, nem o Tibet são conhecidos por estes nomes, dos quaes não tem noticia; e a China chamão Guena, a Tartarea Sopo e ao Tibet Potente
About Sopo (Mongols) as described to Jesuits in Bhutan
Keep in mind
Cacella is reporting what the Bhutanese king told him and matching it to European ideas about Tartars and Cathay; the equations are his own guesses.