Specific word lower-case "announcement" not allowed in Title or Content sections

When trying to save a document, entering the lower-case word “announcement” into any field including Title, Long Title, and Content causes the saving process to freeze and then time-out after a few minutes. Upper-case “Announcement” saves quickly and correctly.

I’ve cleared the caches. It seems like this is a reserved word in the system or something but otherwise I’m stuck. Please assist.

This definitely smells like a mod_security issue. It’s based on rules set by your host.