quadrat (n.)

Proto-Indo-European root meaning "four."

It forms all or part of: cadre; cahier; carillon; carrefour; catty-cornered; diatessaron; escadrille; farthing; firkin; fortnight; forty; four; fourteen; fourth; quadrant; quadraphonic; quadratic; quadri-; quadrilateral; quadriliteral; quadrille; quadriplegia; quadrivium; quadroon; quadru-; quadruped; quadruple; quadruplicate; quarantine; quarrel (n.2) "square-headed bolt for a crossbow;" quarry (n.2) "open place where rocks are excavated;" quart; quarter; quarterback; quartermaster; quarters; quartet; quarto; quaternary; quatrain; quattrocento; quire (n.1) "set of four folded pages for a book;" squad; square; tessellated; tetra-; tetracycline; tetrad; tetragrammaton; tetrameter; tetrarch; trapezium.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit catvarah, Avestan čathwaro, Persian čatvar, Greek tessares, Latin quattuor, Oscan petora, Old Church Slavonic četyre, Lithuanian keturi, Old Irish cethir, Welsh pedwar.

1820 as a shortening of quadrangle (n.) in the building-court sense (in this case "quadrangle of a college," Oxford student slang); also in old slang the quadrangle of a jail or prison, where prisoners take their exercise. By 1880 as short for the printer's quadrat (n.). By 1896 as "a quadricycle, a bicycle for four riders" (quadricycle is attested by 1879, quadruplet in this sense by 1893). As "one of four young at a single birth" by 1951 (in reference to armadillos), short for quadruplet; 1970 as a shortening of quadraphonic (adj.). Related: Quads.