many words have unrelated meanings (like band can mean a strip of cloth or something, or a musical group, etc). But if it helps, a "cape" is an outer layer of clothing, so it's possible the meanings are actually related. Like when someone says to put on another layer of clothing. Once upon a time that layer would have been a cape : )
Great explanation! None come to mind right now, but in english we also have many words that have two unrelated meanings.