The Compendium of Caraka 6.14.6_1

6.14.6_1

tadastyadhimāṃsadeśatayā, &gudavalijānāṃ tvarśāṃsīti saṃjñā tantre 'asmin/sarveṣāṃ cārśasāmadhiṣṭhānaṃ---medo māṃsaṃ tvak ca//

That exists because those are sites of polypoid muscular growths; but in this treatise, the term "hemorrhoids" (arśas) applies to those arising in the rectal folds. And the substratum of all hemorrhoids is fat, flesh, and skin.