Nowadays we tend to think of someone as having a ‘real’ name, with nicknames and diminutives as informal variations on that one official and authentic version of the name. A person’s ‘real’ name is what appears on the birth certificate, of course (and also in the baptismal record, if relevant), and in all subsequent official documents (driver’s licenses, marriage certificates, deeds to property, and so on). Nicknames and diminuitives are for casual, informal use only.
It was different in the nineteenth century, however, when people were much more flexible about name variations (and also about surname spellings, which point is admittedly a bit of a hobbyhorse of mine).
Take, for example, Lillian Doyle. And I call her “Lillian Doyle” because that is the name that I remember her by. Not that I ever met her: she died before I was born. But I recall my father and his sister talking about her, and hers is one of those names that has always stuck in my mind. Dominic Stanton. Evelyn Sullivan. Tommy Burke. Danny O’Neill. Lillian Doyle. A whole cast of colourful characters whom I only “know” by hearsay, or only posthumously, so to speak, but who have always seemed to play an interesting part in the drama (or perhaps comedy?) of my father’s family history.