The article discusses a set of English intensifying adverbs which originate in the spatial domain and share the basic meaning ‘out’: outly, throughout(ly), twert-out, outright and utterly. Most of them developed degree readings in the Middle English period. The semantic associations of the meaning ‘out’, issuing from the container schema (boundedness and negative evaluation), determine the nature and distribution of ‘out’-intensifiers as maximizers with negative semantic prosodies. Syntactically, the adverbs evolve from spatial adjuncts to degree adjuncts and finally to degree modifiers of adjectives, adverbs, and other heads. Their development is viewed as a case of grammaticalization, displaying typical characteristics such as acquisition of more abstract meanings (spatial > degree), persistence, the workings of pragmatic inferencing, subjectification, scope reduction and renewal within the paradigm of maximizers.