Worth noting is that gettext honors environment variables while selecting the language to use: http://www.gnu.org/software/gettext/manual/html_node/Locale-Environment-Variables.html
"When a program looks up locale dependent values, it does this according to the following environment variables, in priority order:
LANGUAGE
LC_ALL
LC_xxx, according to selected locale category: LC_CTYPE, LC_NUMERIC, LC_TIME, LC_COLLATE, LC_MONETARY, LC_MESSAGES, ...
LANG
Variables whose value is set but is empty are ignored in this lookup. "
In short, if you have non-empty LANGUAGE, you may end up with unexpected localization strings. On the other hand, LANGUAGE can be used to define fallback language if some translation is missing.