The key to this idiom lies in the term 灵犀 (líng xī), or “spiritual rhinoceros.” Ancient Chinese legend held that a special type of rhinoceros had a horn with a white line running from the base to the tip. This line was believed to be a channel for magical or telepathic energy, creating a direct, unblocked connection. Therefore, 心有灵犀 literally means “the heart possesses a spiritual rhinoceros horn,” a beautiful metaphor for two minds being directly and intuitively connected.
`心有灵犀` is an elegant but common idiom used in both written and spoken Chinese.