parol (n.)

1610s, "word of honor," especially "promise by a prisoner of war not to escape if allowed to go about at liberty, or not to take up arms again if allowed to return home," from French parole "word, speech" (in parole d'honneur "word of honor") from Vulgar Latin *paraula "speech, discourse," from Latin parabola "comparison," from Greek parabole "a comparison, parable," literally "a throwing beside," hence "a juxtaposition" (see parable).

The sense of "conditional release of a prisoner before full term" is attested by 1908 in criminal slang. An earlier term for a similar thing was ticket of leave.

*gwelə-, also *gwel-, Proto-Indo-European root meaning "to throw, reach," with extended sense "to pierce."

It forms all or part of: anabolic; arbalest; astrobleme; ball (n.2) "dancing party;" ballad; ballet; ballista; ballistic; ballistics; belemnite; catabolism; devil; diabolical; discobolus; emblem; embolism; hyperbola; hyperbole; kill (v.); metabolism; palaver; parable; parabola; parley; parliament; parlor; parol; parole; problem; quell; quail (v.) "lose heart, shrink, cower;" symbol.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit apa-gurya "swinging," balbaliti "whirls, twirls;" Greek ballein "to throw, to throw so as to hit," also in a looser sense, "to put, place, lay," bole "a throw, beam, ray," belemnon "dart, javelin," belone "needle," ballizein "to dance;" Armenian kelem "I torture;" Old Church Slavonic zali "pain;" Lithuanian galas "end," gėla "agony," gelti "to sting."