As part of the Nephite armor listed in Alma 43:19, mention is made of "thick clothing." According to the Works of Ixtlilxochitl, when the Tultecas fought they would put on some sort of long tunics down to the heels, of a thousand colors, embroidered, and very closely woven and thick, so that no matter how hard they would hit each other with the lances -- for these (lances) were what they most used -- they could not pass them (cut them through). [Milton R. Hunter and Thomas S. Ferguson, Ancient America and The Book of Mormon, pp. 274-275]
According to John Sorenson, the "thick clothing" worn defensively by the Nephites seems related to the suits of quilted armor (ichcauipilli) used by the Aztecs and their neighbors. Salt or some such substance was placed between layers of cloth and the combination quilted loosely. This garment could withstand a direct arrow impact, yet it was so light and cheap that the Spaniards themselves adopted it. [John L. Sorenson, An Ancient American Setting for the Book of Mormon, p. 262]
“They Were Dressed with Thick Clothing”
Brant Gardner notes that the "thick clothing" (Alma 43:19) is plausibly a description of a type of body armor best known from Aztec times:
Quilted cotton armor (ichcahuipilliI) was a common element of battle attire in Mesoamerica. It was constructed of unspun cotton tightly stitched between two layers of cloth and sewn to a leather border. The belief that the cotton was soaked in coarse salt to strengthen it derives from de Landa; but this account is unsubstantiated elsewhere, and Gates thinks this is a misinterpretation of taab, "to tie," for tab, "salt," and that the cotton was tied or quilted, not salted.
The ichcahuipilli was so thick (one and a half to two fingers) that neither an arrow nor an atlatl dart could penetrate it. It was made in several styles: a type of jacket that tied at the back, a sleeveless jacket that tied in the front, a sleeveless pullover that hugged the body and reached to the top of the thigh, and a sleeveless pullover that flared and reached to midthigh. (Ross Hassig. Aztec Warfare, p. 88)
This style of protective armor may also be painted on a Maya pot. Reents-Budet describes the scene on this particular pot:
Lord Kan Xib Ahaw takes captives in battle. The victorious warriors are identified by their short-sleeved shirts, three of which are made from jaguar pelts. Perhaps these jaguar tops are a type of body protection stuffed with cotton or reinforced in some other manner similar to the effective armor worn by the later Aztecs and adopted by the invading Spanish in the sixteenth century. (Dorie Reents-Budet. Painting the Maya Universe: Royal Ceramics of the Classic Period, p. 259).
While it would be too precipitous to suggest that the Nephites invented this type of armor, we are certainly witnessing a time period before it had been widely accepted, and thus could be a distinguishing difference between the Nephite and Lamanite forces. [Brant Gardner, Book of Mormon Commentary, [http://www.highfiber.com/~nahualli/LDStopics/Alma/Alma43.htm], pp. 14-15]
Alma 43:19 They were dressed with thick clothing (Illustration): Armor -- Quilted Clothing -- Heavily armed spearman of ancient Chichen Itza, Yucatan. Note the thick quilted clothing, spear and shield. In his headdress are feathers of the sacred Quetzal bird, one of the symbols of the Messiah. [Milton R. Hunter and Thomas Stuart Ferguson, Ancient America and the Book of Mormon, p. 275]