Using Japanese common words for projects is becoming almost cliche these days among software developers. What's next, Kuruma ? Madoguchi ? Unko ?
First of all, it is a platform name (Android) and a language name (Kotlin), joined together and abbreviated. The word "anko" is short and there's no other library with the same name (at least, I didn't heard of one).
Also, it was created to make Android development sweeter with some synthetic sugar^Wanko.
Finally, I just love daifuku.
Alright. I guess it makes sense here.