The design of the Scorpenek droids seen in the latest episode of The Book of Boba Fett is based on concept art for Star Wars: Episode II – Attack of the Clones, as reminded by The Book of Boba Fett production designer Doug Chiang on Instagram. It was ultimately not used in the movie at the time.
It was Chiang himself who came up with this design two decades ago. It was then called the “Annihilator Droid”. Here’s an excerpt from The Art of Star Wars: Episode II – Attack of the Clones:
“One of the lost concepts for Episode II was the deadly, spiderlike Annihilator Droid. “Before the annihilator droid was written out, it was going to be one of the powerful, next-generation droids”, Chiang observed. “What was curious was, George [Lucas] felt there were too many droids so he dropped this, but then a bunch of new robots were created for the end battle. But the Annihilator Droid never came back.””