The word "seal" can refer to a few different concepts. In a general sense, it often means to close something securely, so that it is protected or inaccessible. For example, you might seal a letter by enclosing it in an envelope and sticking it shut. In another context, "seal" can refer to a marine animal known for its playful nature and swimming ability. Additionally, "seal" can denote a symbol or emblem used to authenticate documents.
The word "seal" comes from the Old French "sele," which means a signet or emblem, and from Latin "sigillum," meaning a little sign. The term has evolved over centuries to encompass the various meanings it holds today.