"Remirashi" is a portmanteau of "Remiria" and "Higurashi", which is a species of cicada in Japan. Koakuma was referencing "Higurashi no Naku Koro Ni" (eng: When the Cicadas[the Higurashi kind] Cry), a murder mystery visual novel with the cry of higurashi cicadas being a recurring theme. One of the characters in Higurashi, Rika Furude, often says "Nipaa~~" which literally translates to "big smile" or something. Since "Nipaa~" is exclusively associated with Rika (at least in the western hemisphere), Koakuma made the reference.