Isaiah 49:20 (King James Bible)
the children which thou shalt have after thou hast lost the other shall say again in thine ears …
The King James translation is an attempt to interpret the original Hebrew, which can be literally translated word for word as follows:
again shall–say in–thine–ears children–of thy–bereavement
The hyphens are used to show that each group of hyphenated words represents one word in the Hebrew. The larger passage (verses 19–22) refers to an initial loss of children to be followed by an abundance of children. Here the King James Bible identifies the lost children as “the other”, but the reader can still be confused about what “the other” actually refers to. Joseph Smith, in his editing for the 1837 edition, emended “the other” to read “the first”, which still refers to the original children that were lost. Even so, both readings are difficult because in either case the reader is required to mentally supply children, either “the other children” or “the first children”. The critical text will restore the original text, despite its difficulty. Obviously, the original text of the Book of Mormon followed the King James translation here in 1 Nephi 21:20.
Summary: Restore in 1 Nephi 21:20 the original King James text of “after thou hast lost the other”; Joseph Smith’s change of other to first is an attempt to more clearly identify what “the other” refers to.