小 (xiǎo): Literally means "small" or "little."
丫头 (yātou): This is the key word. Its literal, historical meaning is "slave girl" or "maidservant."
Modern, Figurative Meaning: In modern, colloquial Chinese (especially in northern dialects), "丫头" has completely shed its literal meaning and evolved into a affectionate, familiar nickname for a young girl. It's used by elders, relatives, or close friends to express fondness, endearment, and a touch of playful teasing. It carries a similar feeling to English terms like:
"Kid" (as in, "Listen, kid...")
"Young one"
"Little lass"
"My girl"
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The author uses this nickname instead of her real name ("孟小然") to instantly convey a specific tone and relationship:
To Show Affection and Familiarity: The narrator (or the perspective the narrator is adopting) is speaking about her in a very fond, almost familial way. It's not a formal or distant address.
To Emphasize Her Youth and Naivete: It highlights her character as being young, perhaps a bit impulsive, innocent, or cute in her reactions—like the fact that she "widened her eyes" in surprise.
To Create a Colloquial, Lively Tone: It makes the narration sound more conversational, personal, and grounded, as if we're hearing a story from a close friend or observer.
In Summary:
Think of "孟小丫头" not as a name, but as a term of endearment. The best way to translate the feeling into English would be to use a similar colloquialism.
And I use term 'Our girl' and 'Little lass' for it.
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I pluck this from Novel My VR Games Terrify the World, Chapter Cooking, Coding, and a Company to Build.