Add this text to a plugin file or your theme’s functions file and then change the ’18’ to the id of the category of products you want to apply the filter to.

/**
* Filter woocommerce product titles.
*
* @package Fix
*//**
* Filter the product title by category
*
* @param string $title The title.
* @param integer $id The id.
*
* @return string Filtered title.
*/
function woocommerce_category_title_filter( $title, $id ) {$post_type = get_post_type();if ( ‘product’ !== $post_type ) {return $title;}$categories = wp_get_post_terms( $id, ‘product_cat’ );if ( empty( $categories ) ) {return $title;}

$cat_ids = wp_list_pluck( $categories, ‘term_id’ );

if ( ! in_array( 18, $cat_ids, true ) ) { // 18 is the product category id being filtered

return $title;

}

return ‘Per Day ‘ . $title;

}
add_filter( ‘the_title’, ‘woocommerce_category_title_filter’, 10, 2 );