Ascetic comes from askētikos, a Greek adjective meaning "laborious." Ultimately, it comes from the Greek verb askein, which means "to exercise" or "to work." There aren't many other English words from askein, but there's no dearth of synonyms for ascetic. Severe and austere, for example, are two words that share with ascetic the basic meaning "given to or marked by strict discipline and firm restraint." Ascetic implies abstention from pleasure, comfort, and self-indulgence as spiritual discipline, whereas severe implies standards enforced without indulgence or laxity and may suggest harshness (as in "severe military discipline"). Austere stresses absence of warmth, color, or feeling and may apply to rigorous restraint, simplicity, or self-denial (as in "living an austere life in the country").