The baby was 'fostered' at birth, therefore I presume that the new parents would have christened her as was their want, ie Grace. The "Mac" is most likely a shortened form of her first married name of Macadam.
Does anyone know if children born illegitimate at this time would customarily have had their name entered as that of the mother? As in this case Agnes Graham.
Do you know the names of the 'new parents' who may have been relatives?
Did Agnes/Grace Agnes name a father on her MC?
I'm unsure what exactly you're asking re the name of an illegitimate child?
An illegitimate child could be named with whatever Christian name the mother chose.
The illegitimate child would be given the surname of the mother at the time whether she was single/married/separated/divorced/widowed.
I could elaborate on the above but no point in confusing the issue as it's not relevant at this time.
However, if the father of the illegitimate child was present at the Registering of the child & signed as being the father, the child would be given his surname.
The child would then be indexed with both parents' surnames at the time & if the mother had been previously married then the child would also be indexed under the mother's maiden name too.
I hope the above makes sense but as Agnes wasn't married & the father wasn't present at the registration then the child would automatically be given the mother's surname which would not be classed as a/her maiden name as she was never married.
Only married/previously married women have 'maiden' surnames.
Annie