The source article defines white labeling and names the product categories it is commonly used for (electronics, consumer products, software) under its Common use section, but gives no year or originating industry for the practice itself.
What would resolve this A manufacturing-history or branding-history source giving a specific year, decade or originating industry for when white-label or private-label contract manufacturing first took its modern, named form.
OpenBusiness HistoryWikipedia, White-Label Product