Modern 吃 combines 口, “mouth”, with 乞, which supplied the sound in an older word meaning “to stammer”. In older texts the everyday verb “to eat” was often written 喫. Because the words came to sound alike, 吃 was later borrowed for “eat” and became today’s standard form. So the visible mouth is a useful clue now, but the tempting story “mouth + begging = eating” is a mnemonic, not the securely attested origin.
A piece of culture
Mandarin 吃, Cantonese 食 In Mandarin, 吃饭 (chīfàn) is the everyday way to say “eat” or “have a meal”. Cantonese can read 吃 as hek3, but ordinary speech normally uses 食: 食飯 (sik6 faan6). That contrast is useful, not a mistake—it shows how Mandarin and Cantonese can share writing traditions while choosing different everyday words.
Use it in a real word
吃饭
chīfàn · hek3 faan6
to eat a meal — everyday Cantonese normally says 食飯, sik6 faan6