كُوسٌ

A drum: said to be an arabicized word [from the Persian كُوسٌ, pronounced “ kós, ” but in Arabic “ koos, ” and applied in the present day to a kettle-drum; according to Golius, a kettle-drum that used to be beaten in the camps and palaces of kings]. (S, K.) [The modern plural is كُوسَات.]

Hence, A فَرْسَخ [or parasang, or league, in which sense also it is of Persian origin]: because this is the utmost distance at which may be heard the beating of the كوس. (TA.)

Also, A triangular piece of wood with which a carpenter measures the squareness of wood. (Lth, A, * K.) It is [in this sense likewise] a Persian word. (TA.)