Don't think anyone has posted this yet, but here's their themed names in Japanese:
Ichika 一花 (lit. one flower)
Nitori 二鳥 (two bird)
Mifu 三風 (three wind)
Shizuki 四月 (four moon)
Their surname Miyabi 宮美 can be interpreted as "palace beauties"
edit: ah, the scanlator explained their names in...