An elephant was a large animal native to the African and Asian continents on Earth. They were noted for their characteristic prehensile trunk. (TOS novel: The Rift)

An old human joke ended with the line, "We can't kill a whole elephant for just one steak." David Rabin paraphrased this line while he and Spock were stranded in the desert of Obsidian, instead referring to a boktarik, a native reptile. (TOS novel: Vulcan's Forge)

Hikaru Sulu explained to anyone interested in carving that elephants produced ivory. (TOS novel: The Fearful Summons)

By 2294, James T. Kirk thought of himself as a white elephant. (TOS novel: The Fearful Summons)