The word "拇指" (mǔzhǐ), meaning "thumb", is formed through a direct, descriptive combination of two characters: "拇" (mǔ), which specifically denotes the thumb or big toe, and "指" (zhǐ), which means finger. It is a compound where the first character specifies the particular type and the second provides the general category, creating a literal meaning of "thumb-finger". This construction visually and conceptually identifies the thumb as the primary or prominent digit, with "拇" carrying a connotation of "the chief one" among the fingers.