Online Etymology Dictionary

compassion: mid-14c., from O.Fr. compassion, from L.L. compassionem (nom. compassio) "sympathy," from compassus, pp. of compati "to feel pity," from com- "together" + pati "to suffer" (see passion). Loan-translation of Gk. sympatheia.
compassionate (adj.): 1580s, from compassion. Phrase compassionate conservatism in American political language first recorded by 1992, popularized, if not coined, by Marvin Olasky, University of Texas at Austin instructor.
bowel: c.1300, from O.Fr. boele "intestines, bowels, innards" (12c., Mod.Fr. boyau), from M.L. botellus "small intestine," originally "sausage," dim. of botulus "sausage," a word borrowed from Oscan-Umbrian, from PIE *gwet-/*geut- "intestine" (cf. L. guttur "throat," O.E. cwið, Goth. qiþus "belly, womb," Ger. kutteln "guts, chitterlings"). Greek splankhnon (from the same PIE base as spleen) was a word for the principal internal organs, which also were felt in ancient times to be the seat of various emotions. Greek poets, from Aeschylus down, regarded the bowels as the seat of the more violent passions such as anger and love, but by the Hebrews they were seen as the seat of tender affections, especially kindness, benevolence, and compassion. Splankhnon was used in Septuagint to translate a Hebrew word, and from thence early Bibles in English rendered it in its literal sense as bowels, which thus acquired in English a secondary meaning of "pity, compassion" (late 14c.). But in later editions the word often was translated as heart. Bowel movement is attested by 1874.
piteous: c.1300, from Anglo-Fr. pitous, O.Fr. pitos (12c.), from M.L. pietosus "merciful, pitiful," in V.L. "dutiful," from L. pietas "dutiful conduct, compassion" (see piety).
ruthless: early 14c., from reuthe "pity, compassion" (late 12c.), formed from reuwen "to rue" (see rue (v.)) on the model of true/truth, etc. Ruthful (early 13c.) has fallen from use since late 17c. except as a deliberate archaism.
compatible: 1459, from M.Fr. compatible, from M.L. compatibilis, from L.L. compati (see compassion).
feel (v.): O.E. felan "to touch," from Gmc. *folijanan (cf. Du. voelen, Ger. fühlen "to feel," O.N. falma "to grope"), from PIE base *(s)pol-/*(s)pal- "to strike softly" (cf. Gk. psallein "to pluck (the harp)," L. palpare "to touch softly, stroke," palpitare "to move quickly"). The sense in O.E. was "to perceive through senses which are not referred to any special organ." Sense of "be conscious of a sensation or emotion" developed by late 13c.; that of "to have sympathy or compassion" is from c.1600. Noun sense of "sexual grope" is from 1932; from verbal phrase to feel (someone) up (1930).
mercy: late 12c., "God's forgiveness of his creatures' offenses," from O.Fr. mercit, merci "reward, gift, kindness," from L. mercedem (nom. merces) "reward, wages, hire" (in V.L. "favor, pity"), from merx (gen. mercis) "wares, merchandise." In Church L. (6c.) applied to the heavenly reward of those who show kindness to the helpless. Meaning "disposition to forgive or show compassion" is attested from early 13c. As an interjection, attested from mid-13c. In French largely superseded by miséricorde except as a word of thanks. Seat of mercy "golden covering of the Ark of the Covenant" (1530) is Tyndale's loan-translation of Luther's gnadenstuhl, an inexact rendering of Heb. kapporeth, lit. "propitiatory."