Yatsko (in international transcription:[jɑːc'ko]; in English transcription: [jɑːts'ko]; Russian spelling: Яцко) is a Slavic surname that can be found in Russia, Belarus, Ukraine, the United States, Moldova and some other countries. In English speaking countries it is pronounced with the first syllable stressed [ˈjɑːtskoʊ] and has other less common variants of spelling: 'Iatsko', 'Jaczko'. The surname is rather rare and hasn't been listed among the most common surnames in the above mentioned countries.
V. Dahl, a famous Russian lexicographer in the 19th century, considers 'Яцко' a as a word specific to the dialect of Yaroslavl region that originates from the word 'ятской' ['jɑːtskoi] and gives the following interpretation of the meaning of 'ятской': "a pie eaten with honey; biscuit with butter and eggs cooked in a pot or jar".
A. Superanskaya, a famous contemporary onomastician, thinks that 'Яцко' is a derivative from the first name Yan ['jɑːn] wide spread in Poland and Belarus, whose diminutives are 'Yatsek', 'Yatsko' [1]. The Polish-Belarusian 'Yan' is an equivalent of English 'John' and 'Yatsko' can be considered an equivalent of 'Jonnie'.
The latter interpretation seems much more plausible since many Yatskos living in Russia came from Belarus.
The most famous Yatskos in Russia are Meritorious Artists of Russia Alexandr Yatsko (Александр Яцко) [2] and Igor Yatsko (Игорь Яцко) [3]; Viatcheslav Yatsko, an expert in computational linguistics [4]; Ivan Vasilievich Yatsko, a high-ranking officer in the Russian Imperial Army. The most prominent representative of this surname in the USA is Gregory Jaczko, Chairman of the U.S. Nuclear Regulatory Commission.
The surname must be distinguished from the first name. Prince Yatsko Kepenik mentioned in chronicles as the Chief of rebels who struggled against German invaders in the 12th century [5] is sure to have nothing in common with the contemporary Yatskos because 'Yatsko' was his first name. Actually, 'Yatsko' is an evidence of peasant origin: Russian peasants, who till the abolition of serfdom didn't have surnames, adopted first names as surmanes. This surname has never been registered in the lists of Russian or Polish gentry.