The Swahili were a people, culture, and a language on Earth from eastern Africa.
Nyota Uhura's name is Swahili for "Star Freedom". (TOS novel: Uhura's Song)
Some translations have uhura translating into "truth". (TOS novel: The Starless World)
In 2269, James T. Kirk told Nyota Uhura to send a message to Starfleet Command in Swahili so that the Klingons could not translate it. Uhura replied that even modern Swahili lacked some technical terms, which the Klingons might use to figure out the message. (TOS novel: Spock Must Die!)
Kwaheri was Swahili for "goodbye". Hikaru Sulu offered this to Uhura in 2293. She responded with "Kwaheri". (TOS novel: The Fearful Summons)
In 2371, Benjamin Sisko named his Bajoran lightship Baraka, after the Swahili word for "good fortune". (DS9 episode: "Explorers", CCG set: Tenth Anniversary Collection)