The Bo Y in Lao Cai province of Vietnam claim to have left China 250 years ago to escape oppression by the Han, the dominant people group.  It was probably during the 1797 Nanlang Rebellion, when thousands of Bo Y were brutally burned alive at the stake. 

In China, the Bo Y had a sinister reputation among the other tribes.  In the early 1900's, they were described as being, "Crafty, lying, and dishonest."  But these days the Bo Y have a better reputation.  In fact, they are noted as warm-hearted and hospitable people.