lamb
羜 centers on a young sheep: a lamb. The meaning is specific to that animal.
羜 combines 羊 (sheep) with 宁, which likely contributes the sound. The character is a phono-semantic compound for a young sheep.
The left side 羊 is a sheep, and the right side 宁 looks like a small shelter. Picture a lamb staying close to its pen: 羜 is a lamb.
For チョ, imagine a lamb named Cho who always stays near the shelter: Cho -> チョ, the little lamb.