John Doom said:
[…] Not sure about Kashyyyk, but IIRC it was already considered as a setting for the original SW or mentioned in Chewie’s background.
According to John Doom, Kashyyyk IS mentioned in the OT.
That’s not in the OT.
Well, I didn’t say it is actually mentioned in the movies, just that I remember it was mentioned in the scripts. So today I checked everywhere to find the source of this rumor and found this essay on the development of the Star Wars script:
Chewbacca (now with the nickname “Chewie”) is “an eight-foot-tall-savage-looking creature resembling a huge bushbaby monkey with fierce baboon-like fangs. His large blue eyes dominate a fur-covered face and soften his otherwise awesome appearance.” 140
With his production paintings, Ralph McQuarrie had convinced Lucas to soften the two-hundred-year-old Wookiee’s frightening features and eliminate his clothes, leaving the two chrome bandoliers. 141
Beside the script, Lucas constructed a detailed culture for the Wookiees. They live in giant trees (just like the “Ewoks” in Return of the Jedi) on their homeworld Kashyyyk, and they have their own version of the Force based on their empathy with plant life. Their most sacred custom is the life debt, which Wookiees pledge to those who save their lives. When Chewbacca was saved from Imperial slavetraders by Han Solo, he pledged a life debt to Han, and now he travels with his saviour in order to carry out his sacred obligations. 142 (See also Appendix, p. 54.)