late 14c., "actual, solid," from Latin concretus "condensed, hardened, thick, hard, stiff, curdled, congealed, clotted," figuratively "thick; dim," literally "grown together;" past participle of concrescere "to grow together," from com- "together" (see com-) + crescere "to grow" (see crescent). A logicians' term until meaning began to expand 1600s. Noun sense of "building material made from cement, etc." is first recorded 1834.