[Zigûr]

Originally Posted by Marwhini

I thought that Sauron contrived the Black Speech during the First Age (The First Age was what I thought was referred to as the "Dark Years").

The Dark Years appear to refer to the period in the Second Age in which the Dúnedain were absent from Middle-earth. For instance, Appendix B:

The Second Age
These were the dark years for Men of Middle-earth, but the years of the glory of Númenor. Of events in Middle-earth the records are few and brief, and their dates are often uncertain.

Also, in Appendix A:

After the end of the First Age the power and wealth of Khazad-dûm was much increased; for it was enriched by many people and much lore and craft when the ancient cities of Nogrod and Belegost in the Blue Mountains were ruined at the breaking of Thangorodrim. The power of Moria endured throughout the Dark Years and the dominion of Sauron, for though Eregion was destroyed and the gates of Moria were shut, the halls of Khazad-dûm were too deep and strong and filled with a people too numerous and valiant for Sauron to conquer from without. (Appendix A)

This heavily implies that the Dark Years were after the First Age.

"Akallabêth" also states that the Dark Years were in the Second Age:

the Dúnedain came at times to the shores of the Great Lands, and they took pity on the forsaken world of Middle-earth; and the Lords of Númenor set foot again upon the western shores in the Dark Years of Men, and none yet dared to withstand them.

My understanding of the nature of the "Dark Years" is not based on any argument in any Tolkien wiki. I have never even heard of these "like the Dark Ages after the fall of Rome" arguments before; whoever came up with that theory does not seem to have considered the real evidence that already exists. The evidence suggests that the Dark Years were a time specifically relevant to Men, when the Dúnedain were in Númenor and Men were falling under the influence of Sauron. It seems to be related to this statement from "Akallabêth":

Thus the years passed, and while Middle-earth went backward and light and wisdom faded, the Dúnedain dwelt under the protection of the Valar and in the friendship of the Eldar, and they increased in stature both of mind and body.

To be fair, I previously thought that the "Dark Years" was simply another name for the time of Sauron's dominion in Middle-earth, but it appears that they were not exactly the same thing, although they did coincide to an extent.

Originally Posted by Marwhini

I would think that the period during which Satan Himself ruled in Middle-earth would be considerably "Darker" than a period when his lieutenant was left to meddle in the world.

Maybe so, but it seems that for the majority of Morgoth's latter reign in Middle-earth (after he escaped from Valinor) things were not so dark in much of Middle-earth, as is expressed in "Of Dwarves and Men" in regards to the fortunes of the Dwarves of Khazad-dûm in the First Age:

they were under attack from the Orks of Morgoth. During the War of the Jewels and the Siege of Angband, when Morgoth needed all his strength, these attacks ceased; but when Morgoth fell and Angband was destroyed hosts of the Orks fled eastwards seeking homes.

Of course things were dark for Men in the First Age, what with the corruption of Hildórien and all, but the "Dark Years" seem specifically to refer to this period of the Second Age in which the Men of Middle-earth were "left in the dark" due to the absence of the Dúnedain, lack of relations with the Noldor and Sindar, and the growing power of Sauron.

Getting back on topic, has anyone considered the possibility that Smaug spoke the tongue of Dale? His name, after all, seems to have come from this Dale-language. This is mentioned in The Peoples of Middle-earth:

Smaug, the Dragon's name, is a representation in similar terms, in this case of a more Scandinavian character, of the Dale name Trāgu, which was probably related to the trah- stem in the Mark and Shire.

Interestingly, in that same volume, in "Notes on an unpublished letter" from 1943 Professor Tolkien is discussing Westron, and he states:

In Bilbo's time there was a language very widely used all over the West (the Western parts of the Great Lands of those days). It was a sort of lingua-franca, made up of all sorts of languages, but the Elvish language (of the North West) for the most part. It was called the Western language or Common Speech; and in Bilbo's time had already passed eastward over the Misty Mountains and reached Lake Town, and Beorn, and even Smaug (dragons were ready linguists in all ages)....

Thus perhaps we ought not to be too restrictive when we speculate upon any language a dragon might speak.