Aghaderesi is a village in the Iravan uezd of the former Iravan governorate, later in the former Ellar (Kotayk, Abovyan) district, and currently in the Kotayk province. The provincial centre lies 44 km to the southwest of the town of Ellar, and at a height of 1,450 m above sea level. The name of the village in Armenian is referred to as Agadzor (“dzor” means “a rift” in Armenian) through literal translation.

Along with the Armenians, the village was inhabited by 27 Azerbaijanis in 1831, 14 in 1873, 15 in 1886 and 3 Azerbaijanis in 1897. In the early 20th century, in 1905–1906 the Azerbaijanis were deported from their historical-ethnic land.

The toponym was coined from the words “agha” meaning “a rich man, nobleman or landlord” in Azerbaijani and the word “dere”.

By the decree of the Presidium of the Supreme Soviet of the Armenian SSR dated 4 April 1946, the village was renamed “Katnakhpyur” (Milky Spring). According to the law “On the administrative-territorial division of the Republic of Armenia” dated 7 November 1995, it was integrated into the administrative area of the Kotayk province.

Geographic coordinates: latitude: 40°15′ N., longitude: 44°40′ E.