Ilava is a town in the Trenčín Region, northwestern Slovakia. The name is of uncertain origin. The historic medieval names were Lewe, Lewa, L…Ilava is a town in the Trenčín Region, northwestern Slovakia. The name is of uncertain origin. The historic medieval names were Lewe, Lewa, Lewa de cidca fluviom Vag, later Ilava. The form Illava is known from the 19th century and was used after the Austro-Hungarian Compromise of 1867.