Which country is familiarly known as "The Horn of Africa"?

The Horn of Africa (HOA), also known as the Somali Peninsula,is a large peninsula and geopolitical region located in the easternmost part of mainland Africa. It is the fourth largest peninsula in the world and is composed of Somalia, Djibouti, Ethiopia, Eritrea, and the partially recognised state of Somaliland.[5][6] Although not common, some broader geopolitical definitions include parts or all of Kenya and Sudan. It has been described as a region of significant geopolitical and strategic importance, since it is situated along the southern boundary of the Red Sea; extending hundreds of kilometers into the Gulf of Aden, Guardafui Channel, and Indian Ocean. It also shares a maritime border with the Arabian Peninsula.