The official name of the Soviet currency in Kazakh, Kyrgyz, Tajik, and Uzbek was soum, and this name appeared written on the back of banknotes, among the texts for the value of the note in all 15 official languages of the USSR. The word som (alternatively transliterated "soum" or "sum") means "pure" in Kazakh, Kyrgyz, Uyghur and Uzbek, as well as in many other Turkic languages. The word implies "pure" silver or gold and thus is similar in etymology to sterling.
