Nyan or nya is the Japanese for meow (the cat cry), thus the title means Meow-meow-meow-meow-meow-meow!. The song is an endless loop of Miku saying Nya over and over while making a pounce. Back in 2010, this song was obscure to those outside the Vocaloid and UTAU fandom, until Momo's Version came into light.
On April 5th, Saraj00n uploaded video of a Poptart Cat with Utauloid Momo Momone's Voice on Youtube. The Song became popular, under the name of Nyan Cat. It quickly spread around, and became an internet meme, Appearing in multiple sites, Blogs and Social Networks. It quickly rose to fame over the next few months, and there it started about the origin of the song.
A simple loop animation done by Eromame-sensei. Basically is the same simple dance of the original PV, just drawn in his style and with Tako Luka flying occasionally in the background. It was made as a Special PV for the Exit tunes Album, Vocalonation
Non-Vocaloid Fans and Vocaloid Fans debated on the Originality, some claiming Nyan Cat came first, while the Latter claimed the song was by Daniwell-P, with the Vocaloid Fans stating the correct one.
It caused a flame wars for Japanese Fans on the Supposed Nyan Cat Video on NicoNicoDouga, telling them to "get lost" or to Speak Japanese, as it is customary in NND to speak Japanese.
It was during that time a few people visited Daniwell's Original Video and Momo's Nicovideo, helping it getting a lot views. At the same time, it helped spread the Vocaloid fandom around the West even more.
The confusion died down after a few months prior to the Nyan Cat Video, but it left a bad impression on both sides.
MomomomoP (ももももP) used Momone's Voice to create this cute and knew version. It was this version that was used to co-create Nyan Cat. The Nicovideo was a sight for multiple Users, particularly, users from around the world commented in several languages on the Video. It left Japanese Users Frustrated with the sudden multiple language comments scrolling on screen.