Any NPC who the GM designs for long-term interaction with the players, either as an ally or a nemesis, is given a name. The name is probably the most important part of the NPC, as it encapsulates everything the players will need to get to know this vital character, and allows them to refer to the NPC with ease, as they will no doubt have to do on many occasions in the future.
Conversely, any NPC for whom the GM doesn't have a name ready to roll of the tongue as soon as a player asks is completely unimportant to the plot. Such NPCs can be safely forgotten as soon as you leave their presence, as you'll never, ever come across them again.
Transcript
GM: Watto's shop assistant—
Jar Jar: Issa hesa an alien too?
GM: —a perfectly unexceptional, human boy, enters the room.
Jar Jar: Oooh! What'sa hesa name?
GM: Name? Um... err... Anakin.
R2-D2: Clearly a completely unimportant NPC.
Qui-Gon: Hmm. We should keep an eye on the lad.
Watto: {in background, to Anakin} Coona tee-tocky malia?
Anakin: Mel tassa cho-passa—
Watto: Chut-chut! Ganda doe wallya. Me dwana no bata.
Qui-Gon: Handmaiden! Talk to the kid and pump him for information.
Padmé: And how exactly do you expect me to do that?
Qui-Gon: I don't know. Flirt with him or something.
Padmé: He's nine years old! Do you know how creepy that is?
{beat panel - awkward silence}
Obi-Wan: {inset panel, as he is off-screen} So...
Obi-Wan: Are we in any danger of getting those weapons some time soon?