Source

File: wp-includes/functions.php

function wp_original_referer_field( $echo = true, $jump_back_to = 'current' ) {
	$ref = wp_get_original_referer();

	if ( ! $ref ) {
		$ref = ( 'previous' === $jump_back_to ) ? wp_get_referer() : wp_unslash( $_SERVER['REQUEST_URI'] );
	}

	$orig_referer_field = '<input type="hidden" name="_wp_original_http_referer" value="' . esc_attr( $ref ) . '" />';

	if ( $echo ) {
		echo $orig_referer_field;
	}

	return $orig_referer_field;
}