Background information Edit
The Aaamazzarites were designed by Fred Phillips and Robert Fletcher for The Motion Picture. With the approval of Gene Roddenberry, the Aaamazzarites, as well as numerous other new species in the film, were named by Fletcher and provided a backstory by him. The following is a brief description, in Fletcher's own words:
"AAAMAZZARITES – Therbians from planet Aaamazzara. They generate their own clothing from out of own mouths, like bees making hives. They manufacture everything they use from their own chemistry, from inside their own body, from clothing to furniture. Costumes for film modeled in clay, cast in sheets of foam rubber." (The Making of Star Trek: The Motion Picture, pp. 129-130)
"Anyone who is not an Aaamazzarite will find this race's name much simpler to pronounce if one holds two bumblebees in one's mouth during the attempt. One of a number of insectoid races, they are Therbians from the planet Aaamazzara. An industrious race with a hive intellect, the Aaamazzarites can exist on nearly any planet for they do not depend on surface conditions to provide food or shelter. Everything needed for survival is manufactured through their own body chemistry. The clothes they wear have been produced in a manner similar to a spider spinning a web." 
In an interview appearing in the March 1980 edition of Fantastic Films, part two of "The Star Trek Costumes", Fletcher revealed more information about the Aaamazarites and the design of their costumes. He commented of the aliens, "I guess you could call them bugs. They are very much like our Earth spiders, not in appearance but in the functions that their bodies are able to perform. Everything that they need in way of housing or clothing they sort of spin from their bodies using its chemicals."
In an article appearing in the January 2002 edition of Star Trek: The Magazine Volume 2, Issue 9, entitled "Who is that Alien?", the fact that the Aaamazzarites were referred to as Therbians in Robert Fletcher's notes about the aliens was regarded as "rather confusing."