ascetic (adj.)
1640s, from Greek asketikos "rigorously self-disciplined, laborious," from asketes "monk, hermit," earlier "one who practices an art or trade," from askein "to exercise, train," originally "to train for athletic competition, practice gymnastics, exercise."
ascetic (n.)
"one of the early Christians who retired to the desert to live solitary lives of meditation and prayer," 1670s, from ascetic (adj.).