From Wiktionary, the free dictionary
halt + -ein, which is an Anglo-Norman variant of -ain.
haltein m (oblique and nominative feminine singular halteine)
- (Anglo-Norman) high
- (Anglo-Norman) high; exalted; ranked or lauded above others
c. 1150, Thomas d'Angleterre, Le Roman de Tristan, Champion Classiques edition, →ISBN, page 96, lines 903–4:Issi cum il est reis halteins
e sur les altres sovereins- As he is a high and mighty king
sovereign over all others