A couple of different takes; neither particularly making more sense. AHD:
Tending to irritate; repellent: “He became rebarbative, prickly, spiteful” (Robert Craft).

[French rébarbatif, from Old French, from (se) rebarber, to confront : re-, re- + barbe, beard (from Latin barba).]

From an on-line French dictionary:
rébarbatif
Adjectif

(a) daunting, forbidding

Can't say that I find beards daunting; repellent, yes, 99.99% of the time. I can't--ew--see why on EARTH anybody wouldn't prefer to stroke smooth skin than rough old scraggles.