The word "罄竹难书" is formed through the sequential combination of four characters: "罄" meaning to exhaust or use up, "竹" referring to bamboo slips historically used as writing material, "难" meaning difficult, and "书" meaning to write. These characters together create a literal sense of "even exhausting all bamboo slips would make it difficult to write it all down", directly conveying the idea of an overwhelming amount, typically of misdeeds, that cannot be fully documented.