The compound adjective 'three-pronged' is a transparent English formation. Its first element, 'three', descends from the Proto-Germanic þrīz, which has cognates across Indo-European languages, such as Latin trēs and Greek treis. The second element, 'prong', likely originates from a late medieval Germanic root related to poking or piercing, giving us the image of a sharp, projecting point, as on a fork or antler. The suffix '-ed' is the standard Germanic adjectival ending, used to indicate possession of a quality. Thus, the literal construction "having three prongs" logically extends to describe any strategy, attack, or object divided into three distinct and pointed parts or aspects.

Structure: three (number) + prong (point) + ed (adjective suffix) - three: From Old English þrīe, þrēo, meaning the number after two. Functional role: Numeric root. - prong: From Middle English pronge, meaning a pointed instrument or fork. Functional role: Nominal root. - ed: From Old English -ed, -od, a suffix forming adjectives from nouns, meaning "having the quality of". Functional role: Derivational suffix.