Nyaa comes from nya, the Japanese word used in manga and anime for a cat's meow, similar to how English uses meow. Anime cat girls and kawaii characters adopted it as a signature vocal tic, saying it while posing, purring or acting playful. Clips of the sound spread through anime edits, VTuber streams and soundboards in the 2010s and 2020s, becoming shorthand for cute anime energy online. It remains popular because a single drawn out nyaa instantly communicates character type and mood without needing any dialogue or context.