A building constructed as a symbol which was first called "Tenshu" was the Tenshu constructed in Muromachi-dai (the mansion of the Ashikaga family) which was Gosho (palace) of the 15th Shogun Yoshiaki ASHIKAGA of the Muromachi bakufu (Japanese feudal government headed by a shogun).
そのような象徴的に建てられたものを最初に“てんしゅ”と呼んだのは室町幕府第15代将軍足利義昭の御所であった室町第に建てられた天主であるというものである。