The people of the planet Wehttam were called the Wehttam. Their language was also known as Wehttam.
Despite the planet Wehttam's important part in the Black Fleet Crisis novel series, only the novel Before the Storm makes mention of a group referred to as "the Wehttam." The book's context does not make it clear if this term is used to describe a sentient species from Wehttam or just serves as a name for those who live on the planet. As a point of interest, Wehttam is Matthew spelled in reverse.