'all-green' originates from Old English, specifically the words 'eall' and 'grēne', where 'eall' meant 'whole' and 'grēne' meant 'green'.

'eall' and 'grēne' combined in Middle English in compounds and phrases (e.g. 'all grene' or hyphenated forms like 'all-greene'), and eventually formed the modern compound 'all-green'.

Initially it meant 'completely green (in color)', but over time it evolved to include senses such as 'completely inexperienced' (from 'green' = naive) and, more recently, 'entirely environmentally friendly'.