I’ve had to do that several times before, and i solved it with bogo_language_switcher_links hook, and adding the following in functions.php:
add_filter('bogo_language_switcher_links', 'change_lang_link_names', 10, 2);
function change_lang_link_names($links, $args) {
foreach($links as $index => $link) {
switch($link['locale']) {
case 'en_CA':
$link['native_name'] = __( 'English', 'bogo' );
break;
case 'fr_CA':
$link['native_name'] = __( 'Fran?ais', 'bogo' );
break;
}
$links[$index] = $link;
}
return $links;
}