Since it was described 'Ikko Sennen Muryo Jubutsu' (一向専念無量寿仏) in the sutra "Muryoju-kyo Bussetsu Muryoju-kyo" (無量寿経仏説無量寿経), '一向' Ikko was understood as chanting of the Amitabha's name, from which '一向宗' became a designation used by other sects to refer to the Jodo Shinshu sect founded by Shinran.
これは『無量寿経仏説無量寿経』にある「一向専念無量寿仏」から、阿弥陀仏の名号を称えることと解釈され、そこから「一向宗」が他の宗派より親鸞を開祖とする浄土真宗を指す呼称となった。