Sierra Leone's name can be traced back to the 15th century when Portuguese explorers arrived on its shores. The name "Sierra Leone" is derived from the Portuguese phrase "Serra Leoa," which means "Lion Mountains." The name refers to the mountainous area around the capital, Freetown, which is located on a peninsula surrounded by hills. The Portuguese used the name to refer to the region's mountains, which they believed resembled a lion's profile when viewed from a distance. The name stuck and was later adopted by other European powers that colonized the region, including the British, who established a colony there in the late 18th century. So, the answer is Portuguese.