n. — proprietary
a soft cloth made of cellulose fibres, mainly used for household cleaning.
Type: 1. Origin — The OED-3 suggests that the origin of the name comes from the initial of the brand Johnson & Johnson. Johnson & Johnson Canada invented the cloth in 1963 (see the 2003 quotation and the strategyonline reference). They are reusable, unlike paper towels, but cheaper and more disposable than dishcloths or sponges (see Image 1).
See also OED-3, s.v. "J-cloth", COD-2, s.v. "J-cloth", which labels it "Cdn. & Brit.".
- While J Cloth is the actual trademark name, the hyphenated versions are the more frequent spelling variants.
Images:

Image 1: An advertisement for J-Cloths (Toronto Star 15 Mar. 1966: 32)