Through thick and thin might not be included in traditional marriage vows, but it sends the same message as expressions that are: “for better, for worse; for richer, for poorer; in sickness and in health.” They all basically mean “through the good and the bad” or just “in any circumstances.”You might assume that thick here is good—thick walls, thick wallets, thick scarves, thick stews. The Original Meaning of Through Thick and ThinAccording to the Oxford English Dictionary, usage of through thick and thin was “apparently originally with reference to ‘thicket and thin wood.’” Some sources have taken this to mean that the original phrase was through thicket and thin wood, which people eventually simplified to through thick and thin. Through Thick and Thin to Chaucer, Spenser, and MoreThe Oxford English Dictionary’s oldest reference to through thick and thin comes from “The Reeve’s Tale” of Geoffrey Chaucer’s Canterbury Tales. Edmund Spenser used through thick and thin in Book III of his epic poem The Faerie Queene, published in 1590. The Figurative Thick and ThinIt’s hard to pinpoint who first used through thick and thin figuratively.