Natasha is formed by the root of
Natalya which is "
Nat-" and "-asha/sha", a common ending for Russian pet names. For example, a pet form of
Daria is Dasha, which uses the "
Da-" from
Daria and the ending "-asha", "
Masha" for
Maria and so forth.
Other pet forms of
Natalya can be Natachka, Natanka, etc. There isn't a standard list of pet names for any one given name. Once you get past the traditional nicknames of a particular name, it's customary to "make them up". Any person could have a dozen pet names, if so desired. There's a saying that the more pet names/nicknames people give you, the more they like you. :) Names such as
Tatiana and (Y)ekaterina have many, many nicknames.
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