In the Etymologies, tark derives from Primitive Quendian tāra-khil (roots TUR and KHIL).[note 1] It has been suggested that tarkil means "literally 'high follower' ([since] the Elves referred to Men as followers because they were the Afterborn Children of Ilúvatar)".[note 2]
Quenya
tarcil
proper name. High Man, Númenórean
A term for the “high men”, those of Númenórean descent (LotR/1131). It is a compound of tar- “high” and a shortened form of Hildo “Man”.
Conceptual Development: In the early tales of Númenor from the 1930-40s, Tolkien used the term ᴹQ. Turkil “Great or Lordly Man” in the different versions of the Lament of Atalante (LR/47, SD/246). The initial element of this earlier term was derived from the root ᴹ√TUR “power, control, mastery, victory”, as indicated in The Etymologies from the 1930s (Ety/TUR). The term ᴹQ. Tarkil also appeared in The Etymologies, and the two terms seemed to be equivalent (Ety/TĀ, TUR). In Lord of the Rings drafts from the 1940s, only the term ᴹQ. Tarkil appears (TI/8, 84; WR/310), so apparently Turkil became obsolete.