This is quite a specific question, and may make no sense out of context, but the context may be hard to explain.
If you have a name such as Tertius, which is Latin for "third son", what is an alternative to translating that name to Japanese rather than simply converting the syllables?
To put it another way, what is the Japanese equivalent of a name which means "third son"?
The closest I have got so far is "San-nan", but I'm not practiced enough to know whether this is usable as a name or merely a description.