Hugh Nibley explains:
The Hittite names in the Book of Mormon all come to us in an Egyptianized form, which is what one would expect in Lehi’s Palestine where Hittite names still survived even though Hittite language was probably not used.20 Thus the Nephite Manti, while suggesting the Egyptian Manti, Monti, Menedi, etc., also recalls the Egyptian name of a Hittite city, Manda. A highly characteristic element of Hittite and Hurrian names are Manti and -andi, likewise common in the Book of Mormon. The Nephite Kumen, Kumen-onhi, Kishkumen certainly remind one of the Egyptian-Hittite name of an important city, Kumani; Nephite Seantum is cognate with Egyptian-Hittite Sandon, Sandas; the Jaredite Akish and Kish are both found in the Old World, where they are of very great antiquity, Akish being the Egyptian-Hittite name for Cyprus.21 Most interesting is the Nephite city of Gadiandi, whose name exactly parallels the Egyptian rendering of the name of a Hittite city, Cadyanda.22 It should be borne in mind that one of the great discoveries and upsets of the twentieth century has been the totally unsuspected importance and extent of the Hittite penetration of Hebrew civilization. Every year the Hittites receive new importance in the Hebrew story. The Book of Mormon has not overdone its -andis and -antis!– Hugh W. Nibley, An Approach to the Book of Mormon, 3rd edition, (Vol. 6 of the Collected Works of Hugh Nibley), edited by John W. Welch, (Salt Lake City, Utah : Deseret Book Company ; Provo, Utah : Foundation for Ancient Research and Mormon Studies, 1988), Chapter 22
How would Joseph Smith know to include Hittite names? How would he know about the importance of Hittites in Hebrew history?