As with Queen Mother, is it true that this title has seldom been used as a formal one? It seems that, generally speaking, qualifiers such as "Dowager" and "Mother" have not been used unless absolutely necessary -- such as distinguishing different queens with the same name. We saw this in the case of the United Kingdom for fifty years (1952-2002). Had, for instance, the present British sovereign chosen "Mary" as her regnal name, her mother could certainly have continued styling herself as "Queen Elizabeth": it's just that she would have lost the designation of being Her Majesty THE Queen.
If the current Queen had chosen to reign as Mary III, there would have been two Queen Mary, since her grand mother was still alive.
I believe, then, that DOWAGER QUEEN and QUEEN MOTHER are largely descriptive terms, rather than official titles. Interestingly enough, each involves two nouns, designating two statuses: the former states that a woman is both a widow AND a queen; the latter that a woman is both a queen and a mother of a reigning monarch.
Also, the word DOWAGER, although a noun, can be thought of as adjectival in the context of the term "dowager queen." Likewise the word MOTHER, although a noun, can be thought of as adjectival in the context of the term "queen mother."
All the biographies and films about King Ludwig II of Bavaria seem to refer to his mother, Marie, as "Queen Mother." Interestingly enough, in one of them, the term is hyphenated ("Queen-Mother). Of course, it's an English translation of a text originally written in German. I don't believe, however, that she was ever formally styled thus, despite meeting the conditions to qualify as a queen mother (the widow of King Maximilian II and mother of Kings Ludwig II and Otto). To the best of my knowledge, she was simply "HM The Queen of Bavaria" from 1848 to 1864, and then "HM Queen Marie of Bavaria" from 1864 until her death in 1889. Correct me if I'm wrong.
BTW: nobody ever answered my question on the Franco-Iberian board as to whether the title "La Reine Mčre" got used in royal France. Similarly, I'd like to know whether, in fact, the title "Die Königin Mutter" ever got used in any of the German kingdoms.
There were never any Queen Regnants in Germany or France. Could the mother of a King be Queen Mother? Could Queen Mary have been known as The Queen Mother?