1. So I should have asked you this so that we can determine for sure if this address came from Electrum or not:
Open that watch-only wallet where the address is in and click on the 'Receive' tab. Now find where exactly that address can be found. Is it under the "Main account" branch or is it under "Imported" (do you have an "Imported" there at all)? If it is under "Imported" then it must have been generated outside of Electrum, but then you most probably have the private key there in the wallet and you should be able to send the bitcoins from that address. Otherwise (if it is under "Main account"), it was generated by Electrum and you need to find the seed or the normal (not watch-only) Electrum wallet. When you create an Electrum wallet it shows you the 12 word seed and asks you to write it down somewhere. On the very next step it asks you to type it in again, to make sure you have it. So how did you get through this step? Also, are you sure the wallet you have is watch-only and not a normal wallet (find the address that you sent the coins to and try right clicking and then click "Send From" and see what shows up)?
2. You can use an address generated outside of Electrum by importing its private key. But you say you are unable to send from this address, right? This makes me think that the address is probably not imported. Otherwise it means there is some other issue at hand that we haven't determined yet (we'll go into that if the answer for point 1. above is "Imported").
3. It is possible that you went through bitaddress.org's address generation and then imported the private key that is immediately displayed there. Then you should be able to send from it and the 8-word thing remains unexplained. It is also possible that after the address generation on bitaddress.org you clicked "Paper Wallet", then "BIP38 Encrypt" (this is usually how many people generate encrypted paper wallets) and then entered a passphrase (perhaps the 8 words). Then you may (should) have printed the wallets or kept other copies. But then importing that into Electrum would have been somewhat complicated (you would have gone through something like this:
http://www.thecleverest.com/importing-bitcoin-from-a-paper-wallet-into-electrum/ or you imported only the address and not the private key, which is also complicated, as far as I know) so I think this is unlikely.
4. So one explanation for the 8 words could be that they are the passphrase for a BIP38 Encrypted private key (see 3). Another explanation could be that they are the passphrase for some encrypted Electrum wallet.
5. I assume that by "regular access to the wallet" you mean when you had the normal (not watch-only) wallet that was destroyed when you reformatted your disk, is that right?
By the way, it may be worth it to try data recovery on that reformatted disk. There are a few topics in this section that go into details about that.
I think knowing I generated it from bitaddress ...
I'm not sure that that is the case given that, as I understand it, you can see the address as a receiving address in Electrum and you can see its balance in Electrum but at the same time you are unable to send this balance (points 1 and 2).