Is it normal to have a fear of chains?

Ok, so I was out taking Macro pictures of random things with my new camera. I took a picture of a rusty chain with a padlock on a fence. I just uploaded it to the web, and when I look at it, I get really scared. It's like in my subconscious, I see these rusty chains, expanding, and suffocating me. Maybe I had a nightmare? I was never traumatized as a child.