Where did ChaCha20 and Salsa20 stream ciphers get their names from? This is not a question targeted at a specific crypto implementation, but a question out of curiosity. What's the reason for calling the stream ciphers ChaCha/Salsa? 

I couldn't find any information about this on the Internet. Are those names somehow related to their internal structure, or just to make them stand out from all the other ciphers out there? For example, AES used to be called the Rijndael Cipher (derived from the names of its creators), before NIST standardized it.
idle speculation, my personal favourite! i always thought it was after the dance... 

Salsa dance - see the video (Video demonstrating salsa dancing fundamentals) and jump to ~1min05sec in, the section titled: "side-side-quarter-turns", if you'd prefer to remain seated...

and from (https://en.wikipedia.org/wiki/Salsa20), The Salsa quarter-round function. Four parallel copies make a round.