I like to name it after its done, or at least the general overall feel/climax is set, even if its a work in process. My last composition was nameless till I realised it suited a lot the personality of the friend I´ve been crashing on the last few days, Happy, cheerful, balenced, and somewhat predictable, but also dark, dissonant and weird at times. So I named it after her, a short piece called Sabrina,
Problems with art normally suit all arts. An artist could wake up and say "I will paint a painting called "A night in the clouds"" and then by the end of it relized what he did paint was "The dream of a past longering". Who knows? Naming before seems to me like a good pointer, ut a bad plan to stick to. Live with it, get to know it, and then name it.
Oh, and another curious thing about names. They grow meaning on themselves. A silly simple name could turn emblematic just because its realted to something so great. Language is beautiful and alive. Both music and lyric language... Play with it! =)