'brushy' originates from English, formed by the noun 'brush' plus the adjectival suffix '-y' (meaning 'having or characterized by'). 'brush' itself comes into English via Middle English from Old French 'brosse' (or related forms) meaning 'brush, brushwood'.

'brush' appeared in Middle English as 'brusch, brusche' (from Old French 'brosse'), which yielded the Modern English noun 'brush'; the adjective 'brushy' was formed later by adding the suffix '-y' to create 'brushy'.

Initially related to the noun 'brush' (a bunch of twigs or scrub), the derived adjective came to be used to describe land covered with such scrub or surfaces resembling a brush; the basic sense of 'having brush' has been maintained while application broadened to texture and appearance.