Unless we're supposed to take the iuventus as the genitive with a long vowel and understand some sort of partitive meaning, "a Cantabrian of the youth." Which is decidedly clumsy at best. More amusing still, iuventus is a freaking collective noun, "the youth," not "a youth" or even "a group of young men"-it's the collective entirety of all youth in existence. Iuventus is feminine, not masculine, and therefore cannot agree with masculine cantaber ( cantabra would be the nominate singular feminine). How Cantaber iuventus can even exist is beyond me. But at least the Latin isn't as horrifically awful as Brytenwalda's. Go to mountblade warband/Modules/Napoleonic Wars/Music. Or if they wanted to keep the second declension masculine ending they could just use amnis, Hibernus amnis, which is masculine and not neuter. Now, I play NW with the music disabled for a number of reasons: a few of the selections are. Nominative adjective (in a late form which, although not wrong, makes me sad with a neuter noun! Hiberum (or Iberum if it's absolutely necessary to use that form) flumen would be correct, it's neuter.
The Latin, on the other hand, is less than stellar. Soundtrack called "Iberus Flumen" is also fantastic and it was tough to pick between those two.