Why field tile called tile.

 The phrase "tile drainage" derives from its original composition from tiles of fired clay, i. e., ceramic, which were similar to terracotta pipes yet not always shaped as are pipes. In the 19th century a "C" shaped channel tile commonly was placed like an arch atop a flat tile, denominated the "mug" and "sole", respectively. Today, tile drainage is any variation of this original system that functions in the same mode. Commonly HDPE and PVC tubing denominated "tile line" is used, although precast concrete and ceramic tiles are still used.