Argument that you have never come across the name Idalia or that name is
not in Alexander Beider's dictionary, does not prvide the proof that name
was no adopted by Jewish people.
My mother in law, Ida (Idalia) Abramson came >from the intelectual Vilna
Yiddishkite family. Her mother was the daughter of the originally Vilna
Troupe and later the Warsaw Yiddishe Art Theater (VYKT) actress. I recall
conversation between my mother in law and the Great Dame of the Yiddsihe
Theatre, Ida Kaminska (1966 Oscar winner for the role in "The Shop on the
Main Street), daughter of the famous Vilna actress Esther Rochel Kaminska,
in the Warsaw Jewish Theater during sixties.
Their names- Idalia or Ida was not Americanized version of Yetta. Both
ladies were named as Ida (Idalia) in Vilna by their Yiddishe parents.