mutton dressed up as lamb

The phrase "mutton dressed up as lamb" refers to someone who is trying to appear younger or more youthful than they actually are, usually through their clothing, behavior, or appearance. It implies that the person is attempting to deceive or mislead others about their age or true nature. The metaphor is derived from the idea of mutton, which is the meat of an adult sheep, disguised or presented as lamb, which is regarded as more tender and desirable.