My guess is that the practice was started to emulate royalty, i.e “King Edward IV”, etc. There appear to be far more “J. Winslow Throckmorton III’s”, usually from affluent lawyer families, around than there are “Billy Bob Stumpkicker IV’s”. Same goes for the First Initial Only monicker. Just a touch of familial pretentiousness.
My problem growing up was we moved a lot from the North to the South. I was not only the New Kid, but I was either a “Redneck” or a “Yankee”, depending on which way we had just moved, with an easily mispronounced first name, to boot. Not as bad as "A Boy Named Sue", but it did teach me to adapt.
So, I always used only my middle name, at least until I went off to college and had to get “official”.
What an interesting post! I had forgotten about the medieval practice of men being named after their father so as to indicate the locale of one’s ancestors. Usually, as I recall, they would add the town, resulting in something like “Oliver the Fourth of Gothenberg,” to further identify the person. Last names were rare to almost non-existent, if my recollection is correct.
I can relate to the lawyers’ (usually them) names with an initial letter of the first name, some odd—but pretentious-sounding middle name and then the last name. Whenever I would see one beginning with C. I would bet that it was for “Charlie.”