"To name something is to own it." This is an old idea from the beginning of time. If you can name something, not only can you describe it, you can possibly control it. This why among people who believe in magic and witchcraft, most have a secret or "spirit" name that is only known to them and a select few.
Naming conventions is something a fiction writer needs to keep in mind when introducing his or her characters to the reader. How people name their children and how those children identify themselves will tell a lot about the culture.
In medieval Europe the rise of family names came from people being known by their occupation, a feature, where they lived ("Miller," "Fuller," "Long," "Short," "Bridges," "London," "Longbottom") or who they were related to ("Watson," "Fitzhugh," "Brothersson [that one I don't think I want to look too closely at]"). As a note, in Iceland four members of a nuclear family can have four different last names such as Rorick Erikson, his wife Feya Jorgansdaughter, and their childern Erik Rorickson and Trondi Roricksdaughter (something that gives an Icelandic phone book a slightly higher page count than War and Peace).
The Romans seemed to have a dearth of names that were fashionable over the millennium their republic and empire lasted. To paraphrase Sam Goldwin, "Every Tom, Dick, and Harry was named Gaius." It seems there were only about eight names used for boys and approximately the same number for girls. This led one barbarian chieftain to remark, "The Romans must be a poor people as they can afford so few names to chose from." With everyone named pretty much the same thing, the Romans had to resort to nicknames and qualifiers such as "the elder/the younger," "Black/florid/tall/short/fat," "The African/Thracian/Iberian," etc (which somewhat puts the lie to "Roman efficiency"). The same sort of thing arose among the men who fought the War Between the States. So many were either named John or something outlandish that, like the Romans, most ended up known more by their nicknames (Ulysses Simpson Grant and John Bell Hood were "Sam" as an example) or used their middle name (William Dorsey Pender was known to his contemporaries and history usually just as Dorsey Pender--one of the uncles on my father's side and our cat of the moment were named "Dorsey" for him). In the movie "Zulu," the fact so many Welshmen were named William Jones is highlighted in the practice in Welsh regiments of using a portion of their service number as a qualifier ("2451 Jones" or "Jones 6325"). We ran into something like this in a medievalist group I belonged to. We had three "Roricks," "Rorick Rorickson," "Rorick the Long," and the luckiest of all, "Rorick Joanna's Husband."
Another name use convention I've found notably within three groups is the first two initials used rather than first and second name. Quite often when you run across such, there is a fair chance that the person (male usually) is either a Russian, an Indian (from the subcontinent rather than Amerindian), or worked for the Norfolk and Western Railway.
If you write crime, keep in mind dang near everybody on the street goes by a nickname. Part of this just a natural human affinity for such and part is because there are a lot of dudes out there you just don't want to know your real name. There's also the "AKA" factor (Also Known As). Multiple aliases are the norm (without such, police files that take up three floors could probably be kept in one file cabinet with a drawer left over for munchies and another for girlie magazines). As one cop said, "Everybody on the street's got a name."
There is also the divide between East and West. In eastern Asia, the family name comes first followed by the given names. In my young and more foolish days, this used to trip me up when doing research on that area. As I have to read in translation, whether the family name came first or last (and Lord help me, I even came across one in which it was sandwiched between two given names) seemed totally at the whim of an editor in either New York or London. Before I wised up, I wasted time looking for information on Saburo Sakai under what I thought was the family name, "Saburo"--which is kind of like trying to look up James Longstreet under "Jimmy (by the way, he went by "Pete")."
For the writer, naming characters gives you a certain power. The name can describe their inner person (Dickens' name picks immediately pops to mind), make them ridiculous ("Major Minor," "Private Means,"), show how life treats them (Joseph Heller's "Major Major Major"), or you can honor someone (my naming of spacecraft such as the survey vessel Alfred L. Wegener or the "Hero" class destroyers Kevin Barry and Todd Beamer). The guys in England who translated Rene Goscinny and Albert Uderzo's French comic "Asterix the Gaul" had a field day with this with folks like the Roman commander, Cumulus Nimbus, the over weight Goth, Hemispheric, the Greek Mercenary, Neverataloss, and the confused Egyptian vacationer, Ptennisnet (personally, I think the Druid's name "Readymix" in the American translation used during the comic's short run in U.S. newspapers was funnier than the Brit "Getafix"). I've noticed that Karina Fabian's elves in her Dragoneye, P.I. series have the same lamentable taste in names as Neverataloss' parents.
One thing a writer should probably have little fear of is coming up with a name that nobody would give their kid. Looking at some names will convince you that either all their taste was in their mouth or they must have hated their offspring. I remember a lady who had to go through life as Rose Thorn--naturally, she married a guy named Bush.
3 February 2010: Feast of St. Liafdag of Jutland. Spain recognizes U.S. 1783, Meiji Emperor enthroned - Tokyo 1867, Earthquake - Hawke's Bay, New Zealand 1931, U.S. Marines and Army capture Kwajalein 1944.