[gdw]
Jacerant raises etymological and thus semantic problems. The traditional etymology < Ǧazā’ir (Algiers), originally proposed by Covarrubias in 1611 and adopted by the FEW, comes up against the obstacle of a lack of any obvious historical evidence that Algiers was known for armour manufacture, or indeed well known at all, in the early Middle Ages (DEAF J 228 [Dörr]; Möhren 2006, 5-8). Meyer-Lübke (REW 3947a) and Wartburg (FEW 19,56b) both query the etymology without proposing an alternative. Möhren 2006 takes up a suggestion originally made by Schultz, and suggests derivation from the Dalmatian town of Zadar (formerly Jadera/Gazera/Jazira etc.)
The meaning of jaserant in OF and AN is fairly clear: typically it qualifies hauberc, and the contexts (predominantly epic) indicate that the referent is chain-mail. When attested without hauberc, a jaserant is typically of fer or acier, thus again reinforcing the chain-mail sense (DEAF J 228).
A recent article by Ralph Moffat (curator of European Arms and Armour at the Kelvingrove Museum in Glasgow) presents an important array of technical evidence which points to a different etymology and (originally) a rather different sense for the etymon of jaserant (Moffat 2012): ‘A jazerant is a piece of armour combining mail and padded textiles. It was originally a coat of mail covered with silk-waste and inserted into a brocade garment. The etymology is from the Persian for a war kaftan composed from the words kazh (silk-waste) āgand (stuffed/padded). It passes from Turkish-Arabic sources to French and English. The defining element is the mail often referred to as acier (steel) or fer (iron)’ (p.293). See also Thomas, Romania 35 (1906), 598-601: ‘Ancien français casigan, -ingan, gasigan, -ingan’, and FEW 19,92b.
Möhren, Frankwalt (2006). ‘L’importance de la critique des sources en étymologie’, in: Buchi (Éva) (ed.), Actes du Séminaire de méthodologie en étymologie et histoire du lexique (Nancy/ATILF, année universitaire 2005/2006), Nancy, ATILF (CNRS/Université Nancy 2/UHP), (http://www.atilf.fr/IMG/pdf/seminaires/Seminaire_melh_Mohren_2005-11-03.pdf ), 17 pages.
Moffat, Ralph (2012). Owen-Crocker, Gale/Coatsworth, Elizabeth/Hayward, Maria (eds.) (2012), Encyclopedia of Medieval Dress and Textiles of the British Isles, C.450-1450 (Leiden: Brill), p.293 jazerant.