town, Lombardia ( Lombardy) regione, northern Italy. The town's name derives from the Latin ad decimum, Desio being 10 (decimus) Roman miles north of Milan on the road to Como (one Roman mile was a thousand paces, approximately 4,860 feet, or 1,482 m). In the European Middle Ages the parish had more than 40 churches. Achille Ratti, later Pope Pius XI, was born there in 1857. The town has silk-weaving, food-canning, and metallurgical industries. Pop. (2006 est.) mun., 37,742.