The heart of this paper is a series of etymological lessons. Modern Chinese utilizes two respective characters “吃”and “喫”to represent the meaning of eating. This research addresses the pooling of the usages of the aforementioned two characters from the perspective of semanticity and ancient Chinese corpus. Simplified from “齕”（gnaw, bite, nibble）, “吃”is homographically and homophonically identical with “齕”, but different from the latter in meaning. On the other hand, “喫” originates and is simplified from “齧”（bite, gnaw, erode）. The mutually replaceable usage between “吃”and “喫”stems from the homophonic borrowing between “乞”and “契”.