The words Argent and Encore both come from French (meaning silver - or money more generally - and again or still, respectively), so the album title exhibits a sort of linguistic coherence with the band name. If I'm not mistaken, the words are also alike in that their pronunciations have shifted in the same way: the French words are accented on the second syllable while the English words are accented on the first. Both also consist of only two syllables.
The two words contain the same number of letters, and the patterns of consonants and vowels nearly correspond (the final T and E are the only letters that differ in their types).
I feel it's also worth noting that the initial letters (A and E) form a perfect fifth, which is an important musical interval.
