[Sunred]

Okay, fun fact time. The onis have a specific naming convention going for them.
1. All oni names consist of a word that describes their characteristic and end with the "-ki" suffix, the onyomi style of reading oni(鬼). In the case of Hibiki, it is a combination of hibiki(響き, which means echo) and the -ki suffix. Ibuki also follows the same style of naming convention.
2. If a word that ends with "-ki" is being used to describe the oni, the last syllable is ignored and omitted to avoid redundancies, which is why Hibiki is not called Hibikiki and Ibuki is not called Ibukiki.
3. If the word does not end with "-ki" no omittance is required and simply added together. An example of this is the name Zanki that was mentioned in episode 5 simply being a combination of zan(斬), which means to slash or cut down, and "-ki".