: Tolkien actually contradicts himself on the issue of Dwarven language. They were more open about it in the early ages when they were on friendlier terms with the Elves. But the last great Dwarven linguist among the Elves was Pengolod, who fled Middle-earth after the War of the Elves and Sauron.

The large number of elves that left at the end of the First Age, especially those who had dealings with dwarves in the past, may have also lead estrangement between elves and dwarves. As time passed, those dwarves who had dealings with elves would die. With a scarce number of elves and no dwarves alive who remembered, only stories would remain of what happened during the First Age. Those stories would contain tales of friendship, at first, but also tales of later betrayals.

The estrangement was begining at the end of the First Age. The departure of the majority of the only men the elves truly trusted, the Edain, at the start of the Second Age also added to the estrangement.

From the begining dwarves had delt with men, more than elves had. This continued during the Second Age. The bulk of the men the dwaves delt with during the early Second Age included men that the elves did not know, or trust. Since a large number of men had served Morgorth, this would lead the elves to become wary of these unknown men, and by extension those who openly delt with them.

The elves would no doubt limit the access, of those dealing with unknown men, to elven lands and dwellings. Dwarves dealing with the elves would face these new restrictions. This, coupled with a limited number who remembered the way it once was, would feed the mistrust,and estrangement would continue to grow between the two races.~Aelmer

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: I think the differences go deeper, and for example stem from the way Aule made them. The Dwarves were design to be very tough and unyielding, because Aule knew they would live during the days of Melkor's ascendancy in Middle-earth. Their pride was less derived from the folly of a Fall than that of the Elves.

I think that pride, at least among some elves, may have played a big part in later years. While elves were the First Born, the Dwarf Fathers were in fact the first to live, be self-aware and the first to speak. In some minds of some radical elves, the dwarves may have been thought of as failed usurpers of the elven right of First Born. Usurpers created by a lessor god. A god that went against the will of Eru, much like Melkor.