The word "死缠烂打" is formed by combining two intensifying two-character phrases: "死缠", where "死" (death) acts as an adverb to intensify "缠" (to pester), meaning to pester relentlessly, and "烂打", where "烂" (rotten) intensifies "打" (to strike), meaning to attack or pursue excessively. These pairs are joined to create a single idiom describing persistent and overwhelming harassment or pursuit.