The Mothers are in fact Mantles, distinguishable from the persons who wear them, and the Mantles names are Mother Winter and Mother Summer. Their creation is relatively recent in linear time, following the handover of the Defence of the Outer Gates from the Greco/Roman pantheon to the Courts of Fairie. As a Mantle they are an artificial unit of power and the power used to create them may have come from multiple different sources rather than a single source.
The persons currently wearing the Mantles are therefore NOT necessarily analogous to any mythological being who may have undertaken a similar role to that of the Mantle, they may have been a lesser being who took on the Mantle, such as Mab when she took on the Winter Queen Mantle. PT suggests she comes from later Arthurian Myth, and was originally a mortal. The Kringle Mantle is currently held by Odin, which name would you summon that entity by?
Harry took an educated guess at the being who took up the Mother Winter Mantle, and was close enough to get her attention, if not summon her, but then again Harry has a singular knack for annoying people and getting their negative attention. I think seriously it is a spirit magic talent he isn’t aware of, to know what will get under the skin of any particular individual, and do it either subconsciously or consciously.