The Muslim Somalis of the Horn of Africa speak the Somali language and live in the Somali Democratic Republic (Somalia). There are also substantial numbers of Somalis in neighboring countries: the southern half of Djibouti, the eastern part of Ethiopia, and the northeastern part of Kenya. There are large stable settlements of Somalis in the north of Tanzania and in the Yemeni city of Aden. Although Somalis regard themselves as ethnically one people, there are several subgroups based on patrilineal descent. The term "Somali" is popularly held to derive from the expression so maal, or "come and milk," an expression used among nomads, which alludes to the pastoral subsistence and the Somali ideal of hospitality.