How does refractory make sense? On etymonline.com, refract, when broken down into its etymons, means:
"to bend" (light, sound, heat, etc.), 1610s, back-formation from refraction, and in part from Latin refractus, past participle of refringere "to break up," from re- "back" (see re-) + combining form of frangere "to break" (from PIE root *bhreg- "to break"). Related: Refracted; refracting.
Refractory on the other hand just means stubborn. Can someone explain to me the semantic links between the two?