A hundred years ago, writers and film makers in the West could just say ”poorly known ethnic group X is scary and evil”. Tolkien used his invented goblins and orcs for the same purpose. Thankfully this is considered hate speech today. But it seems that some stories still need tribes of exotic villains. So a new trope has emerged that I like to call ”Actual Ethnic Person Expresses Disgust”.
The Tcho-tcho people were first described in a 1932 story by August Derleth and Mark Shorer, “Lair of the Star Spawn”. They are a race of evil Burmese pygmies. Derleth & Shorer did not make up this fictitious ethnic group out of any concern that peaceful Burmese tribespeople in the real world would read the story and be offended. More likely they had no idea what any real tribe in Myanmar was named. The nasty Tcho-tcho then proved tenacious: they have recurred through the decades in many stories by other writers, notably Lin Carter and T.E.D. Klein.
By the 1990s it became clear that an Actual Ethnic Person had to come in and Express Disgust if the Tcho-tcho people were to remain useful to horror writers. In the 1997 modern-day supplement Delta Green for the Call of Cthulhu role-playing game, Dennis Detwiller et al. explained that though the Tcho-tcho themselves are indeed scary evil pseudo-humans from south-east Asia, everybody else in that part of the world absolutely hates them. In scenarios in the 2018 collection A Night At The Opera, which myself and my RPG group have been enjoying for months now, Shane Ivey and Greg Stoltze specify that the Chinese, the Vietnamese, the Burmese and the Thai loathe the Tcho-tcho. In Stoltze’s neatly structured and unusual scenario “The Star Chamber”, a woman who keeps a bar in a remote multi-ethnic Myanmar village informs the player characters that the Tcho-tcho are terrible monsters — even though a number of them live in that same village.
A really clear recent example of this trope from the screen is found in the fine 2015 horror Western Bone Tomahawk. Here the scary evil people are a race of mute murderous male cave-dwelling cannibals who treat their own women with horrifying cruelty. But they do seem to have been living in that cave for a very long time. And this, the script writer realised, technically makes them Native Americans, which is not good. So there’s a scene in the movie where an Apache man (played by Zahn McClarnon) comments on them and says that the troglodytes are nasty and evil and absolutely not Native Americans. (Even though several of them are played by Native American actors!) The Apache character serves no other purpose in the narrative and is never seen again. Even in our own more enlightened time, once an Actual Ethnic Person has Expressed Disgust, we are free to enjoy the fight against the scary evil people / orcs as if it was 1932.
For a solid summary of Tcho-tcho lore in fiction and RPG materials with references to the literature, see Daniel Harms, The Encyclopedia Cthulhiana. I have the 1998 2nd edition.
Here are my best reads in English during 2019. The total was 41 books of which 44% were e-books. Find me at 
Aardvarchaeology - by Dr. Martin Rundkvist 