mid-14c. (mid-13c. as a surname, Walter le Onorable, also known as Walter Honurable), "worthy of respect or reverence, respectable," also "signifying or rendering distinction or respect; ensuring good repute or honor," from Old French onorable, honorable "respectable, respectful, civil, courteous," from Latin honorabilis "that procures honor, estimable, honorable," from honorare "to honor," from honor (see honor (n.)). Meaning "honest, sincere, in good faith" is from 1540s; sense of "acting justly" is from c. 1600.
"Now, George, you must divide the cake honorably with your brother Charlie."--George: "What is 'honorably,' mother?" "It means that you must give him the largest piece."--George: "Then, mother, I should rather Charlie would cut it." ["Smart Sayings of Bright Children," collected by Howard Paul, 1886]
As an epithet before the name of a peer, Church or civil official, guild officer, etc., from c.1400. As a noun, "honorable person," late 14c. Alternative adjective honorous (Old French honoros) seems not to have survived Middle English. Related: Honorably; honorableness.