Hey there, Incredible. Welcome to the wonderful place that is LucasForums.
Number Two isn't meant to be Spanish, or Italian, or anything for that matter, really. As for his name, well... generally, the character of Number Two was intended to be the assistant to the villain (hence him being Darth Vapour's right hand man) and hence his name being 'Number Two'.
Nobody thinks it's strange because it's funnier that way. But here's a snippet that was cut from Tierra de los Muertos (for some reason I'm trying to write it into a book):
A few minutes later found Miguel and Tomas sitting across from… well… a mortal, in the deserted break room of the DOD. Tomas went to take a nervous draw of his cigarette, but the mortal pulled a face.
‘That stuff’s not good for you, you know.’ He said. ‘Well… yeah.’
‘So…’ Miguel said, in an attempt to start a casual conversation. ‘You’re… you’re alive.’
The mortal wiggled his fleshy fingers, and Miguel hardly repressed a shudder. ‘Seems so.’
‘How’s that working out for you?’ Tomas asked.
The mortal shrugged. ‘Until now, rather well.’
‘Good, good. You in good health?’
‘Aren’t likely to die soon?’
‘Errr… not that I know of.’
Tomas shrugged. ‘Oh well. Never too late to start.’
‘What’s your name?’
‘Mine? Tomas. Most people call me Red. He’s Mikey.’
‘It’s a long story. Your name?’
‘Really? That’s your name? What sort of name is that?’
‘It’s an even longer story.’
To put it short, Number Two is Number Two.