With the continuous effort for a harmonious coexistence with nature in human settlement, theories for ecological design and urban sustainability are proposed and developed. However, in 2014, a new concept called 'ecological wisdom' was proposed with the baseline that knowledge of ecological design should be gained from past sustained examples as ecological design problem spaces are unbounded. How can ecological wisdom from designs be acquired for reuse? The purpose of this research is to propose a conceptual framework for the acquisition of ecological wisdom and develop a detailed externalization methodology (a process of making tacit knowledge into explicit knowledge). Then, to see if it works or not, the methodology is applied to private Korean gardens of the Joseon Dynasty, which are renowned for being 'naturalistic'. First, references from knowledge management (KM) are reviewed to claim that externalization step is necessary for the knowledge cycle of ecological wisdom. Then, for externalization, four steps are presented: (1) Case definition; (2) case deconstruction into geometric data and environmental data; (3) similarity calculation for each data types; and (4) matrix correlation between similarity matrices from geometric data and similarity matrices from environmental data. When the above externalization method is applied to 35 cases of private Korean gardens, yearly average temperature and proximity to the nearest river were the most correlated natural factors in terms of architectural spatial relationship in Korean gardens.