Where does "Pages Similar" link text come from?

[costume]

When I type in a competitor name (in this case "buycostumes") Google shows several related websites in it's "Pages Similar to..." section at the bottom of the page:

My question, can anyone tell me where the text comes from that Google uses as the link.  Our competitors have nice branded links and our is just a keyword.  I can find nothing on-page that Google is using so it must be coming from someplace off-page, but where?

[Malarowski]

Did you do a lot of anchor text linking for 'costume'?

[costume]

No.  Funny, that was the first thing I thought after checking Title/METAs.  I'm wondering if this is getting pulled from some directory/index like ODP (no we're not in ODP).

[Develop41]

Looks like Google is picking the keyword meta tag as the anchor text and description tag for the detail. Though it might be picking the most relevant keyword, on the basis of page content, from the list instead of the first one everytime.

Just something I found checking the pages above. The anchor texts are strangely the very first in the list of keywords.