More effort ...
The song is "Ievan Polkka", also known as "Leva's Polka" due to a spelling error. It's a Finnish folk song made popular by the group Loituma. Recently it has gained popularity online due to a clip of the song (the clip featured in this video) being set to a video loop of an anime girl spinning a leek - this clip is known as Leekspin.
Now, the interesting thing is that while the song is in Finnish, the middle part is improvised on the spot by one of the singers and is essentially gibberish - this part of the song is the part featured in the Leekspin clip and in this video. Due to Finnish sounding like gibberish to most people who don't understand it, many people mistakenly believe this middle part to be Finnish as well.
Which brings me at least to the review: The lyrics featured in this video are indeed correct, but they match the whole song, not the part featured here. The lyrics for this middle part can obviously not be found as the part is improvised at each performance. Not only are the lyrics wrongly applied to the song here, but the overall quality of this video is low, even for an animutation. I encourage the author to put more effort into his work in the future.