The written Japanese language consists of three alphabets. Katakana is one of them, made up of simple boxy letters representing sounds. This alphabet is used to write words borrowed from other languages, and certain trademarked names, like names of Digimon.
Below, you see how the names of Piyomon's evolution line are written in katakana. Romanized versions of the katakana letters can be found below each letter.
If you've never run into Japanese before, you might be wondering why Pyocomon and Birdramon's names are written the way they are in Roman letters instead of 'Pyokomon' and 'Baadoramon'. Well, the Japanese and Roman alphabets are very different, and in Japanese, words are written exactly the same way they're pronounced. If Birdramon was written with the katakana letter 'bi' (pronounced 'bee') instead of 'ba', her name would not be pronounced correctly. As for Pyocomon instead of Pyokomon? Well, you can easily turn Ks into Cs when Romanizing.
Names such as Birdramon are NEVER written as 'Baadoramon' in Roman letters, even when Roman letters are used in Japanese.
Am I confusing you yet? I'm horrible at explaining things - if you want to know more about the wonderful world of Japanese writing, go search the web or something!
All Digimon names end with 'mon'. This is short for 'monster'. Let's take a look at what the parts before the 'mon' of Piyomon's evolution line's names mean!
Nyokimon: A Japanese sound effect for plants sprouting. If the Japanese were to make a comic of Jack and the Beanstalk, the beanstalk would most likely go 'nyoki nyoki' as it sprouted. Nyokimon probably got her name for being just that - a sprouted seed Digimon.
Pyocomon: 'Pyoko' is another sound effect, this time for quick bouncing. While the reason behind Pyocomon getting her name isn't as obvious, it still makes sense - she's a lively and happy little Digimon.
Piyomon: One more sound effect, for chirping this time! Birds in English comics may go 'cheep cheep', while Japanese ones go 'piyo piyo'. Piyomon is a bird Digimon, so it fits.
Birdramon: Two English words were used this time - bird and dragon. Sure enough, Birdramon is a bird, and quite a monstrous one at that!
Garudamon: Garudamon's name comes from Garuda, a bird-man hybrid creature from Hindu and Buddhist mythology.