Analysis of information sources in references of the Wikipedia article "Andorra la Vella" in English language version.
The word vella has been translated into both English and Spanish as meaning 'old'. In fact, vella is a corruption of the Latin word villa, meaning 'city'. Thus Andorra la Vella merely means 'the city of Andorra'
"El sobrenom la Vella, és a dir, la vila, li fou afegit posteriorment per tal de distingir la vila del conjunt del territori homònim i potser també per a subratllar-ne la capitalitat" English: "The nickname La Vella, that is, the town, was later added to distinguish the town from the whole of the territory [of Andorra] and perhaps also to emphasize its role as the capital.