Tonya

In 2018, 38 is the most common age for an American (U.S.) Tonya* who is registered female with the Social Security Administration. It is the 444th most common female first name for living U.S. citizens.

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*as a first name, not a nickname.

The celebrities from English-speaking countries named Tonya/ Tonja and their birth year. Compare it with the year of translation of "Doctor Zhivago" novel into English (1958) and screen adaptation (1965). And notice, that no one person was born before 1958! So it is quite clear that this name came to USA and other countries from the Pasternak's creation.
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Tonja Buford-Bailey, American athlete born 1970
Tonja Christensen, American model 1971
Tonya Cooley, American model 1980
Tonya Crowe, American actress 1971
Tonya Edwards, American basketball coach 1968
Tonya Engst, American technology writer 1967
Tonya Harding, American ice skater 1970
Tonya Knight, American bodybuilder 1966
Tonya Massaline, American basketball player 1977
Tonya Pinkins, American actress 1962
Tonya Rouse, Canadian television journalist 1975
Tonya Schuitmaker, American politician 1968
Tonya Verbeek, Canadian wrestler 1977
Tonja Walker, American beauty pageant contestant 1960
Tonya Lee Williams, British-Canadian actress 1958.

All the famous persons named Tonya were born since 1958. Especially many ones since 1965. So I think its popularity comes from Pasternak's novel and its screen version "Doctor Zhivago". One of the characters is Antonina or Tonya (wife of Zhivago).

In Russian words, it is written "Тоня"

It is Russian diminutive of Antonina.