That's not what it was. "ncr" was "No Country Redirect".

When you were in a different country (e.g., India), and you typed in google.com out of habit, it would recognize your IP-geo and redirect you to the country-specific domain (e.g., google.co.in).

If you really just wanted google.com for whatever reason, then you'd type google.com/ncr. It then wouldn't redirect you based on your IP-geo, and you'd stay on google.com.

In other words, google.com/ncr _always_ redirected you back to google.com. Then, and now.