weak child; frail child; gangly child
Colloquial, often mildly teasing or self-deprecating term for a child who is physically weak, thin, or pale, likened to a bean sprout.
Our kid is a weakling and catches colds easily.
I was a frail child when I was little, but now I'm sturdy.
Standard kanji-kana spelling; もやし (bean sprout) + っ子 (child).
Rare variant using 萌 for もやし; not commonly used.
From もやし (bean sprout) + っ子 (child), referring to a child as thin and pale as a bean sprout. The exact origin is uncertain, but it is a colloquial coinage.