The noun forms of the verb to excoriate are excoriator, excoriation, and the gerund, excoriating.

It is actually corium which means skin. Because the medical definition of excoriate is to tear of or take away skin. To cause to take away skin.

condemn, reprobate, decry, objurgate, excoriate, denounce

excoriate, peel, skin, scalp, lash, whip, scathe, scarify, scold, scourge, thrash, beat, blister, deprive, strip, steal, snatch,

"Excoriate," not "excorist," means to criticize or condemn severely. It refers to a strong expression of disapproval or reproach towards someone or something.