A little more on translating Roman Catholic parish records from the French:
Anonyme = Nameless, or Unnamed. Generally with reference to the lack of a first or given name, and most frequently found in infant burial records.
Inconnu/Inconnue = Unknown. As in: of unknown parentage, and generally with reference to the lack of a “legitimate” or legally recognized surname. So: de parents inconnus = of unknown parents. Found in both infant baptismal and infant burial records. Note: In many baptismal records for “illegitimate” children, the mother’s name is both known and given, but due to her unmarried status, the child’s surname will still be given as “Inconnu” (or “Inconnue” for a female).
A child could be both, of course, both unnamed (“anonyme”) and of unknown parentage (“inconnu/inconnue”). And if you spend any amount of time perusing the RC parish registers, you will undoubtedly come across a burial record such as the following, from the Mission of Ste. Anne at Calumet Island (L’Île du Grand Calumet), Pontiac Co., Québec:
S. [Sépulture] 26.27 Deux enfants AnonymesLe douze Septembre mil huit cent quatre ving cinq par nous prêtre soussigné ont été inhumés dans la cemetière de cette paroisse les corps de deux enfants anonymes nés de parents inconnus ondoyés à la maison. Présents Francis Kelly et Arthur Grandpré qui n’on pu signer.[Burial 26.27. Two Unnamed InfantsThe twelfth of September one thousand eight hundred and eighty five, by we the undersigned priest were buried in the cemetery of this parish the bodies of two unnamed infants of unknown parents who were privately baptized. Were present Francis Kelly and Arthur Grandpré, who could not sign.]
Btw, ondoyé (ondoyés in the plural) à la maison is one of those phrases that is a bit difficult to translate literally from the original, owing to the accretion of several centuries of accumulated meaning. Basically, it means baptized privately, or at home, without a priest, in an emergency situation where a child was not expected to live.
Such records are unspeakably poignant; and always make me wonder about the complex human dramas buried beneath the brief and bare-bones recital of the facts of birth and burial.
But to return to the two relevant terms: while both refer to a lack of a name, and while both might be applied to the same person in the case of a burial of an unnamed child of unknown parentage, the two words anonyme and inconnu are not at all synonymous.
For genealogical purposes:
“Inconnu/inconnue” will almost invariably alert you to an “illegitimate” or “born out of wedlock” scenario. If a child was registered as having no legally recognized surname, then he or she had no legally recognized (i.e., married to the child’s mother) father.
“Anonyme” in and of itself, on the other hand, suggests nothing of the sort. “Anonyme” is most frequently encountered in infant burial records; and often refers to a stillborn infant, or to an infant who died so shortly (a day or two or so) after birth that the parents had not yet given him or her a first name. In many (and perhaps the majority of) such cases, the child was “legitimate,” and “born of the lawful marriage of [John Smith] and [Mary Jones],” but died too soon to have been given a first name. Hence “Anonyme [Smith]” and etc.