Ar-Abattârik, like the eighteen rulers of Númenor before him, took the Sceptre with a Quenya name, Tar-Ardamin. In private, though, the King's Men called him by a name in their own Adûnaic language: Ar-Abattârik. This King was the last to follow the practice of using an official Quenya name. His son Ar-Adûnakhôr abandoned the old traditions, and used Adûnaic in his official name.
 Other Versions of the Legendarium
It should be said that there is some doubt over the character of Ar-Abattârik. He is listed in the detailed annals of The Line of Elros as the son of Tar-Calmacil and father of Ar-Adûnakhôr, but in Appendix A I (i) to The Lord of the Rings, the relevant section of the King-lists appears like this: '...Tar-Calmacil. After Calmacil the Kings took the sceptre in names of the Númenorean (or Adûnaic) tongue: Ar-Adûnakhôr...' It seems most likely, as Christopher Tolkien suggests, that this omission is probably a simple mistake, and that Tar-Ardamin or Ar-Abattârik should appear in the list at this point.