Rather than an essay on a literary or academic keyword, this string is a technical payload designed to manipulate a database query. Specifically, it uses a UNION ALL statement to append a row of null values to the original query results, which helps an attacker determine the number of columns being returned by the server. The -- at the end is a comment syntax used to ignore the rest of the original, legitimate code.
If you are looking for an essay on the or how developers can defend against these vulnerabilities using prepared statements and input validation, I can certainly provide that. {KEYWORD}) UNION ALL SELECT NULL,NULL,NULL,NULL,NULL-- ttSb