WordPress at a glance
function is not described

wp_get_original_referer() WP 2.0.4

Retrieve original referer that was posted, if it exists.

No Hooks.

Return

String|false. Original referer URL on success, false on failure.

Usage

wp_get_original_referer();

Changelog

Since 2.0.4 Introduced.

Code of wp_get_original_referer() WP 5.7

<?php
function wp_get_original_referer() {
	if ( ! empty( $_REQUEST['_wp_original_http_referer'] ) && function_exists( 'wp_validate_redirect' ) ) {
		return wp_validate_redirect( wp_unslash( $_REQUEST['_wp_original_http_referer'] ), false );
	}

	return false;
}