c. 1300, pitous, "merciful, full of pity" (a sense now archaic; OED's last citation for it is in 1855); also "arousing or deserving pity, such as to excite compassion, lamentable, sorrowful," from Anglo-French pitous, Old French pitos, piteus "pious; merciful, compassionate, moved to pity; pitiful" (12c., Modern French piteux), from Medieval Latin pietosus "merciful, pitiful" (source also of Spanish piadoso), in Vulgar Latin "dutiful," from Latin pietas "dutiful conduct, compassion" (see piety). Also in Middle English "godly, righteous, devout, pious." With irregular development of form (according to OED the regular phonetic development from the French word would be *pitous). Related: Piteously; piteousness.