The word sole can refer to something being the only one of its kind or the exclusive option. For example, if you have the sole responsibility for a project, it means you are the only person responsible for it. Additionally, "sole" can refer to the bottom part of a shoe or foot.
The word “sole” comes from the Old French word “sole,” meaning “only” or “single,” which in turn comes from the Latin word “solus,” meaning “alone.”