Here in the original manuscript, Oliver Cowdery initially wrote the name Coriantumr phonetically as Coriantummer. Then he immediately corrected the spelling of the name by rewriting the whole name inline as Coriantumr. There is clear evidence that Oliver was a little exasperated by the correct spelling since he wrote the final r of Coriantumr with a large flourish. He never wrote any of his other r ’s this way in either of the two manuscripts. And this reaction on his part is not surprising since no name or word in English ends in mr.
In order to get this spelling down correctly, Joseph Smith must have read off the spelling of the name letter by letter. (A careful syllable-by-syllable pronunciation of the name could not have distinguished between the alternative ways of spelling the last syllable of the name, as mer, er, or r.) This example provides strong support for what witnesses of the translation claimed, that Joseph would spell out the strange Book of Mormon names when they first appeared in the text since the scribes would not have known how to spell most of them. For a complete discussion of this evidence for the spelling out of Book of Mormon names (but not recognizable biblical names), see the section under volume 3 that deals with the spelling of names.
The name Coriantumr appears 76 times in the text, 64 times in reference to the last king of the Jaredites (who is mentioned 62 times in the book of Ether and twice in the small plates of Nephi, namely, in Omni 1:21). There is another Coriantumr in the book of Ether, mentioned only once (in Ether 8:4). Here in Helaman 1, the name occurs 11 times in reference to the Coriantumr who led the Lamanites in attacking the city of Zarahemla; this Coriantumr was a Nephite dissenter and a descendant of Zarahemla (as explained here in Helaman 1:15). Under the assumption that the small plates of Nephi were translated last, this instance of Coriantumr in Helaman 1:15 is the first occurrence of the name in the text. The end of the name is spelled as mr in the manuscripts (13 more times in extant portions of 𝓞 and every time in 𝓟).
This spelling suggests the possibility that one other name in the text could be in error— namely, the name Moriancumer may be a mistake for Moriancumr:
𝓞 is not extant here. According to 𝓟, the earliest extant source, the name Moriancumer ends in er, not r. The critical text will assume that Moriancumer is correct, even though this could be an error for Moriancumr. For discussion of whether this name should be spelled as two names (as suggested by the spelling Morian cumer in 𝓟) or as one word (the spelling of all the printed editions), see under Ether 2:13.
Summary: Maintain throughout the text the spelling Coriantumr, the immediately corrected spelling in 𝓞 for Helaman 1:15; this occurrence of the name was apparently the first time Oliver Cowdery encountered this name as scribe for Joseph Smith’s dictation; all other occurrences of this name in both manuscripts and in the 1830 edition are consistently spelled this way.