Monkey Brand soap was introduced in the 1880s as a household scouring and polishing soap, in cake/bar form. A firm owned by Sidney and Henry Gross, had produced and sold the soap in Philadelphia, USA. The soap's highly abrasive agent was pumice.
Lever Brothers bought the company in 1899 and transferred the production of Monkey Brand soap to Port Sunlight. The name ‘Benjamin Brooke’ (hence Brooke's Monkey Brand) was used to promote the Monkey Brand soap both in the States and in Britain.
In George Bernard Shaw's "Pygmalion" and the musical based on it ("My Fair Lady"), Henry Higgins tells his housekeeper to take Eliza Doolittle upstairs and clean her up, and to use "...Monkey Brand, if it won't come off any other way." In the movie version, the line is changed to "...sandpaper, if it won't come off any other way."