Han character 脅

It means “flank” in an older sense and “threaten” in threat words. In an episode of the Zuo Zhuan, an ancient Chinese historical chronicle, 駢脅 describes closely joined ribs; the episode is dated 637 BCE. The Eastern Han dictionary Shuowen Jiezi (100–121 CE) defines 脅 as “two flanks” and analyzes it as 肉, the body or flesh element, plus 劦, a sound-bearing component.

Chinese usage extends from the body to a side position, then to pressuring or threatening someone. Japanese dictionaries also record the older flank sense; 脅 appears in words for menace and coercion, and in verbs for threatening or startling someone. The surrounding word decides which layer is meant.

Why do I see 脅, 脇, or 胁?

胁 is simplified Chinese; 脇 is a separate, related character. Traditional Chinese writes 脅; simplified Chinese writes 胁. In Japanese, 脇 is used for a side or flank and is historically tied to 脅’s older flank sense, while 脅 appears in threat words. These forms are related, not interchangeable.

Mandarin and Japanese assign 脅 different readings and build different words from it, so a lone glyph cannot settle which language or word is intended.