Creating a directory for a vocabulary term? Background:

I've opened a new vocabulary named "bc" (an acronym for "Blog categories).

The problem:

Anytime I go to the webpage of each term of this vocabulary, the url is sitename.com/term. INSTEAD OF sitename.com/bc/term

This is because when I first built the site, I disabled the option (somehow, it was a long time ago) to create folders for vocabularies.

What I need is to add a folder only to that vocabulary, i.e a way to make terms of this vocabulary to appear under sitename.com/bc/term.

How can this be achieved?

Note: I've already tried to give a pattern, like bc, [bc], [bc]/. None of these helped.
I would bet that you have the module Pathauto enabled. It allows you to create path aliases for mach of your site stuff like nodes and taxonomies. Go to Configuration > Search and metadata > URL aliases > Patterns. That's where you enter the alias patterns for content, taxonomies, etc.   Set the default alias to [term:vocabulary]/[term:name]

It should be mentioned for any case that the default Drupal path for taxonomy terms is taxonomy/term/[term:id]