For many centuries, it was the tradition for the Kings and Queens of Númenor to take their names in the Quenya tongue. As the Númenóreans became estranged from the Elves and Valar, this practice began to decline. The first sign of this was in the twenty-eighth century of the Second Age, when the King was first known informally by a name in his native Adûnaic tongue: Ar-Belzagar, though he officially maintained the High-elven form, Tar-Calmacil. This convention was continued by his son, whose Elvish name was Tar-Ardamin, though he was known to his supporters as Ar-Abattarîk.
Tar-Ardamin's Heir took matters a stage further, when he actually took the Sceptre using his Adûnaic name, Ar-Adûnakhôr, the first time this had been done in Númenor's history. This name, meaning 'Lord of the West', traditionally referred to the Valar, and was considered by many to be blasphemous and ill-omened. So, despite Ar-Adûnakhôr's hatred of the Elvish tongues (he went so far as to ban their teaching) his name was still recorded in the Scroll of Kings in High-elven form: Tar-Herunúmen.