Himni was one of the four sons of Mosiah who went on a mission to the Lamanites (see Mosiah 27:34; Alma 22:35; 23:1; 25:17; 27:19; 31:6). According to a FARMS article, the name Himni is clearly Hebrew and is represented by the unvocalized form, Hmn on two Israelite seals. The first, from the eighth century B.C., was found at Megiddo in the Jezreel Valley. The other is from the first half of the seventh century B.C.
Because the seal inscriptions do not have vowels, we cannot know precisely how the name is to be read. The Bible knows of a non-Israelite Haman from the time of Esther, and Heman was a noted poet and musician in the time of David and Solomon. The vowel at the end of Himni suggest that it is a gentillic form, meaning "Hemanite." [FARMS, "What's New at Farms: Excerpts from the Insights newsletter and the Journal of Book of Mormon Studies.]