castigate (v.)

1610s, "one of the hereditary social groups of India," from Portuguese casta "breed, race, caste," earlier casta raça, "unmixed race," from Latin castus "cut off, separated" (also "pure," via notion of "cut off" from faults), past participle of carere "to be cut off from," from PIE *kas-to-, from root *kes- "to cut." Caste system is recorded from 1840. An earlier, now-obsolete sense of caste in English is "a race of men" (1550s), from Latin castus "chaste."

Of the castes, the first three are the natural and gradually established divisions of the Aryan invaders and conquerors of India; the fourth was made up of the subjugated aborigines. The Sanskrit name for caste is varna, color, the different castes having been at first marked by differences of complexion, according to race, and in some degree according to occupation and consequent exposure. [Century Dictionary, 1895]

c. 1300, purgen, "clear of a charge or suspicion," from Anglo-French purger, Old French purgier "wash, clean; refine, purify" morally or physically (12c., Modern French purger) and directly from Latin purgare "cleanse, make clean; purify," especially in reference to the body, "free from what is superfluous; remove, clear away," but also figuratively "refute, justify, vindicate," from Old Latin purigare, from purus "pure" (see pure) + root of agere "to set in motion, drive; to do, perform" (from PIE root *ag- "to drive, draw out or forth, move").

By mid-14c. as "to cleanse (a person or soul) from sin or moral defilement; to cleanse, clear, purify" (metal, etc.), also medicinally "to cleanse the body or digestive tract by a laxative, diuretic, or emetic." The figurative sense of "make ideal or pure, rid of objectionable elements or members" is by 1580s. Related: Purged; purging. The Latin verb is also the source of Spanish purgar, Italian purgare.