You may be surprised to learn that rebarbative traces back to the Latin word for "beard" - barba - making it a very distant relative of the English word beard. But there is some sense to the connection. After all, beards may not be repellent, but they can be prickly and scratchy! Another descendant of Latin barba is the English word barb, which can refer to a sharp projection (as found on barbed wire) or a biting critical remark, both of which can discourage others from getting too close.
there are aspects of that writer's personality that any reasonable person would regard as rebarbative, but we're just reading his novels—not marrying him
Recent Examples on the WebOne wonders why a skinny, rebarbative marionette should be getting so much attention. Joan Acocella, The New Yorker, 6 June 2022 But Krugman can also sound like a cross between a bloodthirsty Robespierre and a rebarbative GIF. Sebastian Mallaby, The Atlantic, 5 Feb. 2020
Word History
Etymology
French rébarbatif, from Middle French, from rebarber to be repellent, from re- + barbe beard, from Latin barba — more at beard