The original text shows variation between afraid and nonstandard fraid. The standard afraid is found in every passage (seven of them) that quotes from the book of Isaiah (the King James Bible consistently has afraid, never fraid ):
In all these examples, the expression is of the general form “be afraid”.
In nonbiblical passages in the Book of Mormon, there are four instances of fraid in the earliest text and two of the standard afraid:
Note that the two cases of afraid are of the general form “be afraid” (just like the seven cases in the biblical quotes), but the four cases of original fraid occur in the more specific expression “be exceeding fraid”. Thus there is a systematic difference in the usage for afraid and fraid in the original text.
The emendation of fraid to afraid has been very unsystematic in the printed editions; I list here which editions made the change to afraid:
Except for the first case, the RLDS text retains the original fraid, while the LDS text now has only afraid. Note, in particular, that for Alma 43:21 the 1837 edition reverted to the original fraid, a restoration of the reading in 𝓟, which implies that Joseph Smith, the editor for the 1837 edition, did not consider fraid as nonstandard. Of course, in the 1800s the form fraid was very common in colloquial and nonstandard speech, as it is even today. The critical text will restore the four instances of original fraid in the Book of Mormon text.
The Oxford English Dictionary, under frayed, lists examples of fraid from about 1300 on, including these examples from Early Modern English:
In these examples, fraid is modified by a preceding adverbial element (so, more, or as), which seems to have favored the omission of the initial a in fraid. One could argue that we have a similar kind of preceding adverbial, namely exceeding, in the four Book of Mormon instances of fraid. In the nine original cases of afraid, there is no preceding adverbial that modifies afraid, thus allowing more readily the initial unstressed a of afraid.
Summary: Restore the four original instances of fraid, all in the expression “ were exceeding fraid”: Alma 43:21, Alma 47:2, Alma 58:24, and Helaman 4:3; otherwise, the text has afraid (nine times), all without any preceding exceeding.