Originally it was a part of the pun that made fun of various sects saying 'Believers of Jodo Shinshu Sect don't know about the manners of Buddhism, those of Hokke Sect have no backbone, those of Zen Sect have no money and those of Jodo Sect have no mercy."
元来は「門徒もの知らず、法華骨なし、禅宗銭なし、浄土情なし」という各宗派を揶揄する地口の一句。