In Internet of Things (IoT) era, electronic textiles (E-textiles), which combine various functional devices on a fabric, have attracted attention. Among various components for E-textiles, the human-machine interface device, for example, a keyboard, is one of the most important parts. The triboelectric nanogenerator (TENG) can be a powerful sensing component for the interface device due to its cost-effectiveness, design flexibility and self-powered operation. Previous studies reported fabric-based sensor devices with TENG, but as yet, no device that harnesses commercial compatibility with the textile industry has been reported. It is timely to explore a low-cost TENG-based keyboard made completely of commercial fabric for early commercialization. This paper proposes a TENG-based wearable keyboard that uses only cheap commercial fabrics. Each cell in the proposed keyboard generates electrical signals according to an external touch without any power supply. After an appropriate filtering process, the proposed keyboard can detect a key stroke without any ambiguity. We verify the keyboard operation by typing a word and playing music. The material dependency of the proposed keyboard is experimentally validated with various material pairs. Finally, the endurance of the proposed keyboard against folding, repeated touches and washing is experimentally confirmed for actual applications in a real environment.