From 猫(ねこ) (neko, “cat”) + 吸(す)い (sui, “sucking, 連(れん)用(よう)形(けい) (ren'yōkei, “stem or continuative form”) of the verb 吸(す)う (suu, “to suck”).”).
猫(ねこ)吸(す)い • (nekosui)