(Kiyone literarly stealing her name from tenchi's mother in a rare 1996 hasegawa doujinshi)
Answer: It's a close call really... but both came out much earlier in japan then the media available in the west would have you believe so it has always been a heated subject.
Kiyone Makibi made her first animated appearance in the music video for Magical Girl Pretty sammy that was featured on the Tenchi Muyo Sound File collection that was released in 1994.
But before that she debuted in 1993's, Hexagram of love,
The first novel in the Naoko Hasegawa Tenchi series.
But what about Tenchi's mother Kiyone, who is named Achika in every other canon? Well now you're asking the question that answers both, who came first and why didn't he use Kiyone instead of Noike in OVA3.
Well in winter of 1993 Kajishima contributed two pages to the Doujinshi Chousen Ame 4.0 that hinted at his plan for ova 3
Here we can see Kiyone Masaki next to Yosho's First wife, Kasumi.she is even named Kiyone
The other page clearly shows Noike. It says something along the lines of:
This Is Mashisu and Noike Sakazua, These two are former partners of Mihoshi's.
Mashisu will be getting married to Mihoshi's brother.
And Noike continued to show up in Kajishima's doujins long after OVA2's end,
This is her seto and Mashisu's OVA 2 style design from Tenchi Shuuhou 1996
by the way OVA 3 originally supposed to be a part of OVA 2 and OVA 3 was supposed to include the story for 4... both 2 and 3 were unexpectedly shortened leading to things being cut.
Here is an original story board from AIC sketchbook 7 from the end of here comes jurai where after Azusa left earth tenchi would be approached by Kiyone (Actually Tennyo) and it would have ended on a cliffhanger but they changed it when they were notified that they wouldn't be getting any more episodes.
But why do they both have the same name? All of the Tenchi characters are named after places in Okayama. They are named after Kiyone Station.
And really that's all there is to it.