Sufi (n.)

member of a Muslim mystical order, 1650s (earlier Sufian, 1580s), from Arabic sufi, literally "man of wool" (i.e., "man wearing woolen garments," as opposed to silk), from suf "wool." According to Klein, so-called from the habit of "putting on the holy garment" (labs-as-suf) to devote oneself to mysticism. Related: Sufic.