Is the phrase "treasure trove" redundant ?

TYWKIWDBI has a "treasure" category with 29 posts, at least a half-dozen of which use the phrase "treasure trove", so the question was of some interest to me.  Here are the question and answer, as explained by Ben Zimmer in the On Words column at the NYT:

Since a trove is defined as ‘a store of valuable or delightful things,’ isn’t treasure trove redundant? Has anyone ever spoken of a garbage trove?’’

Treasure trove ultimately goes back to a Latin expression, ‘‘thesaurus inventus,’’  ...thesaurus simply means ‘‘treasure’’ or ‘‘treasury’’ ... The inventus part means ‘‘found,’’ so the entire phrase referred to a rediscovered deposit of precious items without any clues to its owner...

In Anglo-Norman... ‘‘thesaurus inventus’’ turned into tresor trové... adapted by English tongues into something more manageable: ‘‘treasure trove.’’

...Meanwhile, the ‘‘found’’ meaning behind trove (related to the modern French word trouvé) was forgotten, allowing English speakers to reinterpret the structure of the phrase. Instead of trove being understood as an adjective modifying treasure, it came to be thought of as a noun, one that eventually could stand on its own without treasure...

So rather than being needlessly wordy, treasure trove is the etymologically complete phrase, misconstrued over time as a noun-noun compound rather than a noun followed by an adjective. Because of this, some historically minded quibblers even assert that there’s no such thing as a trove. But it’s not surprising that trove has been given a second life as a noun, since adjectives don’t typically follow nouns in modern English...

Interesting. You learn something every day.