<!-- Line 1 above will get the tag name for every tag on the site and set them to the site_tags variable. Each tag object contains both the tag name and a list of the associated posts. This capture statement is all on one line so that the commas can reliably be used as delimiters. Line 2 creates the tag_words variable that is a sorted array of the tag names. -->

{% capture site_tags %}
{% for tag in site.tags %}
{{ tag | first }}
{% unless forloop.last %},{% endunless %}
{% endfor %}
{% endcapture %}
{% assign tag_words = site_tags | split:',' | sort %}