This is just a summary from my previous comments, but I'm ready to formulate an answer now.
My recommendation is to use multiple tags, rather than combining them into a dual purpose tag.
Consider questions about the following:
- C'est la vie
- hors d' oeuvres
- Je me lance, vers la gloire
- Hasta Mañana
- pronto vs. ASAP
- Feliz Navidad, prospero ano y felicidad
Conceivably, this could lead to six different tags (one for each of these):
I think it would be better to keep this down to four tags, and put two tags on each question:
The difference between four and six may seem trivial, but the savings become more significant with more languages. If we were to repeat this process for German, Arabic, Italian, and Japanese, and do this with other tags such as phrases and slang, things would really get out of hand.
Bottom line: I think it's better to have N+M tags, and combine them as needed, instead of NxM tags, and account for every possible combination.