That's Grainger's translation, it's nearly three hundred years old. It was first published 1759 if I remember right, and it's frankly not a very good translation. The line is at the beginning of Book 1, Elegy 10:

Quis fuit, horrendos primus qui protulit enses?/ Quam ferus et vere ferreus ille fuit!

Who was it, who first brought forth horrid swords [ensis is the epic word for a sword, as opposed to the prosaic gladius]? How wild and truly iron he was!

There's nothing wrong with the Latin here. It's quite nice, actually. The elegaic verse structure is well placed, the first line is elegantly spondaic except for (of course) the fifth foot and the emphatic first foot, and the second line is a perfect elegaic line. It also contains a rather witty pun on ferus, "wild, savage," and ferreus, "made of iron." The couplet is bracketed by quis and quam, which have similar initial sounds, and by the use of fuit, coming full circle. The pun on ferus and ferreus is skillfully separated and prevented from exhibiting a rather clumsy alliteration by the inclusion of et vere. Other interesting word choices include enses instead of gladios, which would've broken the meter and which is decidedly prosaic--elegaic couplets may be for elegy, but the first line is still a hexameter verse, and often you'll see epic terms dropped in there for effect

There's nothing wrong with this verse, Latin verse just worked differently than English verse. English couplets generally rhyme, they use frequent alliteration, and poets of Grainger's time often liked to reverse the predicate and subject for suspense (and to imitate classical poets). Latin verse is not bound by any of this. Latin is a synthetic language, so it has much freer word order, and the use of inflection to indicate grammatical case means that rhyme and alliteration are really rather easy. Rhyming verses are so easy in Latin that in verse it's often deliberately avoided, although it's fairly common in prose. Horace, for example, in Odes 1.9, deliberately uses the plural lacertis when he really wants lacerto (since the bracelet in question is obviously not worn on both arms) to avoid rhyming the end of three lines (intimo, angulo, lacerto) in immediate succession. Latin elegy rhymes quite often, but usually within the same line, usually rhyming an adjective in the same case as its noun. We have internal rhyming here, in fact: vere and ille and of course ferus and ferreus. While I'm thinking of it, the poem displays the same tendency that Horace has in the line I just mentioned--Latin verse will often poetically use singular for plural and vice versa. Here we have horrendos enses, an accusative plural for the singular horrendum ensem, which is what you might expect logically (especially with the primus). But it's perfectly good verse structure to use a singular for a plural or a plural for a singular. Alliteration is also relatively easy in Latin, and long strings of alliterative sounds were often thought to be deliberately archaic in verse--Tibullus thus skilfully breaks up primus protulit and ferus ferreus fuit while keeping them close enough in the meter to produce an alliterative pattern. Likewise his separation of quis and quam is equally skilled, linking the two lines and invoking the first from the second.

There's nothing wrong with this couplet. Grainger was a little free and archaic with his translation, but the English language doesn't work the same as Latin and Latin verse structure is not the same as English's. And this is only looking at the conventions of the syntax itself, I only briefly mentioned Latin meter at the beginning there when I said the first line was nice and spondaic. But if we were to go further Latin meter is totally different from English. For one thing it was quantitative, not stress-based, and the iambic stressed meter that is so pleasing to English ears (and which is what Grainger has written in) was not especially pleasing to Latin speakers, who reserved it for satire (for reasons I won't get into). Tibullus wrote his elegies in, well, elegaic couplets, and the way those work is totally different from English iambs (the descending action of the second line of the couplet is lost entirely in Grainger's translation, which bothers me, it makes this sound like epic...)