I don't know if /r/AskHistorians or /r/AskReligion would have been better but I feel that this sub would give a more balanced answer.

I was reading Carlo Ginzburg's book The Cheese and the Worms about a 16th century miller named Menocchio who is on trial for heresy in Italy. During his interrogation it comes out that he read several books that negated or challenged the Catholic Church's teachings on religion.

There was a paragraph or two when describing the Virgin Mary that stuck out to me and I wanted to see if this theory had any basis in historical fact or was just a theory that sprang from the book Menocchio had read.

"An he explained that Mary 'was called a Virgin, having been in the temple of virgins, because there was a temple where twelve virgins were kept, and as they grew up they were married off, and I read this in a book caled Lucidaria della Madonna.' This book, which he called the Rosario elsewhere, was probably the Rosario della gloriosa Vergine Maria by the Dominian Alberta da Castello. Menocchio would been able to read in it: "Contemplate here zealous soul, how after making an offering to God and to the priest St. Jaochim and St. Anne left their most precious daughter in the temple of God, where she was to be cared for with the other virgins who had been dedicated to God. In that place she dwelt in sublime devotion contemplating diving things, and she was visited by the Holy Angels, as though she were their queen and empress, and she was always engaged in prayer.'"

What I got from this is that "Virgin Mary" was a title that Mary was given or associated with due to her being raised in the Temple of Virgins. In Ginzburg's book he also discusses Menocchio's beliefs that Mary could not have bore a child and remained a virgin and that Jesus was a man like anyone else.