The phrase 难辞其咎 is formed by the sequential combination of four characters: 难 (difficult) modifies the verb 辞 (to decline), creating the core meaning "difficult to decline"; the possessive pronoun 其 (his/her/its) connects to the noun 咎 (blame), specifying "his blame". Together, the literal construction "difficult to decline his blame" functions as an idiomatic unit meaning one cannot escape responsibility.