It's been ages when I was told about this, but I believe it is not clan specific. More so, it has to do with the spoken language - White Hmong versus Green Hmong. The Green Hmong are "forbidden" to say or speak the words, "Tsuv tum - tiger bite." to/towards another person, especially when angered, agitated, or out of condemnation. If spoken, that person is "cursed" and will eventually be attacked/killed by a tiger at some point. That is what I recall or was told. (Most likely it is just a Hmong/Mong "village/urban legend" is my guess/opinion.)