CanonCat seems to be missing in language files, and can't be translated.
It's displayed in BE product listing, when 'Force Canonical Category' is selected.
BE/views/product/tmpl/default.php L180-187:
<!-- Category name -->
<td><?php
echo $product->categoriesList;
// show canonical category if set
if(!empty($product->product_canon_category_id) && $product->product_canon_category_id > 0){
echo '<p style = "color:#ff0000;">CanonCat: ' . $product->canonCatIdname.'</p>';
}
?></td>