carma (2) noun "helm" (helmet) in Carma-cundo ("k") "Helm-guardian" (PM:260). Notice that in PE17:114, Tolkien indicated that he rather wanted carma to mean "tool" or "weapon", leaving the status of carma "helmet" uncertain. Possibly shortened to -car in the names Eldacar (Elfhelm?), Hallacar (Tall-helm?) Cf. also cassa in Etym.
Quenya
carma-cundo
proper name. Helm-guardian
carma
helm
carma
noun. helm
A title of Minalcar as the regent of Gondor (PM/260). This name is a compound of carma “helm” and cundo “guardian”. Elsewhere cundo means “prince” or “lord” (Ety/KUN, PE17/117). This might still apply here, since Minalcar was heir to the throne. Furthermore, the crown of Gondor was originally a helmet (LotR/1043 note #1), so perhaps: Carma-cundo = “Crown Prince”.