The word 牛蛙 is formed by combining the character 牛, meaning "cow" or "ox", with the character 蛙, meaning "frog". This creates a compound term where 牛 acts as a modifier to 蛙, specifying a type of frog that is large or robust, directly translating to "bullfrog". The meaning is derived from the literal senses of both characters, with no phonetic or abstract elements involved.