Yestonians
Yestonians was a derogatory epithet for historically ethnic Estonians brought from Russia to Estonia after World War II to staff the political structures of Soviet Estonia with cadres loyal to Moscow. While their ethnicity was Estonian by descent, they grew up in the Russian/Soviet environment, which meant that for many, the primary language was Russian, which made them prone to apply Russian-language pronunciation rules in their Estonian-language speech.
The term thus relates to and derides the heavy Russian accent of these people and their practical inability to speak Estonian. In particular, the word "Estonians" was mispronounced from eestlased to jeestlased [yeestlɑsed], due to the iotation of the letter E characteristic in Russian, serving as the origin of the epithet.
While some of them tried to Estonianize, such as Ivan Kebin, who renamed himself to Johannes Käbin and notably improved his command of Estonian, most others remained Russian by culture and language.
In the 21st century the term jeestlased is also applied to Russian migrant workers in Estonia.
Accent
Their application of Russian pronunciation rules and subsequent mispronunciation of the beginning vowel lettered 'E' in Estonian words into "ye" in place of the plain 'E' — turning Eesti, eestlane and eestlased into Jeesti, jeestlane, and jeestlased. This also happened with other words beginning with the vowel 'E', because it looks the same as the Cyrillic letter Е, which is pronounced as "ye" in Russian, while the letter Э is pronounced as a plain "e".In the 19th-century Russian Estonians were called Естонцы, whereas in modern Russian the word is эстонцы.
Party makeup
As Mart Laar wrote, the membership of the Communist Party of Estonia in the year 1946 was 52% Russians, 27% local Estonians, and 21% "Yestonians". Moscow was distrustful of local communists ; and by 1952, the upper ranks of CPE had eventually become occupied by Russians and Yestonians. The reason was the suspicion that the local Communists, being born in independent Estonia, could have some nationalism in them. During the Khrushchev Thaw, the number of ethnic Estonians in the CPE gradually increased, especially in lower ranks, but still in 1966, the CPE Central Committee had only about 27% of local Estonians.Another demographic distinction between native and "Russian" Estonians was age. In hopes of gaining more autonomy within the Soviet Union, many young Estonians joined CPE around the year 1956, while Yestonians were mostly of older generations.