Faint-hearted and Weak knees

Faint-hearted adjective - Lacking conviction or boldness or courage.

Weak knees and faint-hearted are semantically related. In some cases you can use "Weak knees" instead an adjective phrase "Faint-hearted".

Faint-hearted and weak knees are semantically related. Sometimes you can use "Faint-hearted" instead an adjective phrase "Weak knees".