Pokemon name meaning:
ゲコゲコ gekogeko – alternative frog sound
月光 gekkou – moonlight
甲賀流 kouga-ryuu – The school of Kouga: an ancient school of ninjutsu.
The relevance of moonlight here is the ninja’s tendency to operate at night and the fact that the Pokemon has now added the dark type to its water type.
Members of the Kouga school of shinobi (ninjutsu) were trained in disguise, escape, concealment, explosives, medicines and poison. They were experts in techniques of unarmed combat (taijutsu) and in the use of various weapons.
The last officially known Soke of Kouga-ryuu was 14th headmaster Fujita Seiko (1898-1966). He taught prior to World War II, and earned such a reputation that he was inducted into teaching for the government during the war. He continued to teach privately after the war, and had many students who are still alive today.
Gekogeko is less familiar than the well-known kerokero as a frog-sound. Could there also be a side-reference to the similarly splay-fingered, huge-eyed gecko?