I recently recovered a document containing information relating to some BTC I purchased in 2015. I only have: a passphrase/password, an 18 word mnemonic phrase(the majority of which are not in the BIP39 wordlist, nor the electrum old/new wordlists, e.g. mccartney, hopkinton), and the address: 1CfadqyBDRPt62S9UvBHDPtqRu2kSvwPPu. I idiotically forgot to add what wallet I used, so I'm a bit stuck.
Any ideas about what the mnemonic could be for?