Earther
From Memory Alpha, the free Star Trek reference
Earther or Earthling was used as a deregatory term for Humans in the 23rd century.
The Gorn captain referred to James Kirk as an "Earthling." (TOS: "Arena")
Korax, a Klingon officer visiting Deep Space Station K-7 in 2267, referred to the Starfleet officers there as "Earthers." (TOS: "The Trouble with Tribbles")
A young Spock was called "Earther" by his Vulcan playmates because he was half-Human. (TAS: "Yesteryear")
