The quote you provide gives the answer to your question. The two French words, voir and voire, are homophones, but they mean two different things, and have different (Latin) etymologies. While the legal phrase is usually spelt "voir dire" because of the confusion in meaning described by the quote, it is the word "voire" that is meant, and this word derives from the Latin "verum" meaning truth. Blackstone, knowing his Latin, correctly translated the phrase as "seeing the truth". The French verb "voir" derives from the Latin "video" and is unrelated to "verum". However, because the two are homophones, the legal phrase in question is open to misinterpretation.