cuento chino

Literally, “Chinese tale”. The origin of the expression is unclear, however, there are two possible folk etymologies:

• From the book The Travels of Marco Polo by Italian explorer Marco Polo: Returning from China to Italy, the traveler told stories of mythological animals and incredible fables from such Asian region that were not very believable and unrealistic; therefore, many of these passages were classified as "a Chinese tale" to damage the credibility of these chronicles.
• Another theory suggests it originates in 1847s Cuba, from the Chinese immigrants of the time. In order to continue having cheap labor, the Spanish colonists went to China and promised housing, clothes, work and food to those who would follow them to the Caribbean island. The work they promised was hard but, according to the contractors, well paid. However, they were deceived, victims of "a Chinese tale" that cost the lives of many immigrants who never found their way back.[1]

cuento chino m (plural cuentos chinos)

1. tall tale
2. (idiomatic) baloney, bull, nonsense, hogwash

• “cuento chino”, in Diccionario de la lengua española, Vigésima tercera edición, Real Academia Española, 2014