This paper explores the development and establishment of intensificatory tautology (specifically, size-adjective clusters, e.g., “ great big plans,” “ little tiny room”) in the history of English. The analysis suggests that size-adjective clusters appear in the Late Middle English period as a result of the functional-structural reorganization of the English noun phrase. It is only towards the end of the Early Modern English period that they start to become (relatively) productive in the language, and in Present-Day English that they acquire a wide(r) intensifying functional range (i.e., adjective modifier, emphasizer, degree intensifier) and become associated with informal, spoken-based registers. More broadly, the paper suggests that more research is needed as regards the role of collocation in processes of intensifier creation in the noun phrase and, more generally, as regards how collocation interacts with word-formation processes in this context.