Ryoko=魉呼的汉字意思。

[dongyun]

魑魅魍魉，魉呼（Ryoko）名字取自这个成语中的魉字，意思是能召唤来鬼。
魉皇鬼（Ryo-ohki）意思是鬼中的皇者或是王者

[Dr.Soviet]

[dongyun]

Ryoko，Her name and ghost-related

[akirac]

Yeah her name is ghost-related. Actually Ryoko said 魑魅魍魎 (Chi-mi-mou-ryou) in episode4. 魑魅魍魎 (Chi-mi-mou-ryou) means "kind of monsters arise from spirits"
Also these pronunciation was introduced to Japan from China around 7th to 8th century so it may be different from Chinese pronunciation.
Ryoko said like

"I'll show you good thing why I am called Ryoko. I can summon 魑魅魍魎 (Chi-mi-mou-ryou) from anything."

then she summoned monster in episode4 of OVA but this setting is almost forgotten by Japanese fans too haha.
魎 (Ryo) means monster arise from spirit, 呼 (ko) means calling, so Ryoko means calling monster.
In case of 魎皇鬼 (Ryo-ohki), 皇 (ou) means emperor, 鬼 (ki) means Oni.
This method is called Ateji. It makes Japanese pronunciation correspond letters to make words.

[Y_Anthony_Who]

I always wanted a better explanation of that part in episode 4! Thanks!