Please, you can't compare random names of planets to something as intriguing as "witches" or the "Nightsisters". No way you can drop those names without further explanation. That would be like dropping the term "midichlorians" into TPM without any further exposition about them. Imagine that: "He has the highest concentration of midichlorians I've seen in a lifeform. It's possible he was conceived by them". ...& then no other mention. Audiences would be thinking "Wtf?" for the rest of the film.