Yes, there are some words that are not available; but this is actually not a restriction of Contact Form 7, but a restriction of WordPress.
If you post an input field with a name that is the same as a parameter name already used in a WordPress query, WordPress will confuse them, so you can’t use that name.
The followings are parameter names that WordPress uses in a query:
For example, ‘name’ is used in the query, so ‘name’ is not available for a field name. The best practice in avoiding unavailable names is adding a prefix or suffix to the name, for example, use ‘your-name’ or ‘name-1234’ instead of ‘name’.