This WordPress filter and function can be used to sort posts by the second word in the title.
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// CUSTOM QUERY FILTER //
/////////////////////////
function orderby_lastname($orderby_statement) {
$orderby_statement = "RIGHT(post_title, LOCATE(' ', REVERSE(post_title)) - 1) ASC";
return $orderby_statement;
}
// add filter with function before args
add_filter( 'posts_orderby' , 'orderby_lastname' );
// add this when query is done to prevent filter from running everywhere
remove_filter( 'posts_orderby' , 'orderby_lastname' );