1 Nephi 17:5 includes one of only several words defined in the Book of Mormon:
And we did come to the land which we called Bountiful, because of its much fruit and also wild honey; and all these things were prepared of the Lord that we might not perish. And we beheld the sea, which we called Irreantum, which, being interpreted, is many waters.
Why would Joseph Smith take the risk of giving the interpretation of a word? Wouldn’t that open him up to being proved wrong?
The Book of Mormon Onomasticon offers several (Semitic and Egyptian) etymologies which mean “abundant watering of completeness”, “fully abundant waters” or “great watercourse of all”.
What are the odds the interpretation given would match up to very plausible translations?