You need to add the new words to the language.php of the language/s you are interested in.
If I add a new menu entry "Moon", it will not get translated to any other language unless that word appears as a new line at the corresponding language.php file translated accordingly.
Add by hand as many new lines to that file as needed in order to have those strings translated.
And please, if this works for you, could you please add that information at the Documentation? (wherever you would have expected to find it)
Thanks in advanced!