I doubt that since Bitcoin isn't the first cryptocurrency, it has surely be mentioned before. Perhaps it was written 'crypto currency' or
'crypto-currency' but pretty sure it already does before. I admit I tried to search quickly with google anything before Feb 2008 but didn't find. Same with Archive.org
But then I remembered a document from NSA. References listed below are surely worth to read since it has a high chance to get the word in.
1. Stefan Brands, Untraceable Off-Line Cash in Wallets with Observers, Advances in Cryptology CRYPTO '93, Springer-Verlag, pp. 302-318.
2. David Chaum, Achieving Electronic Privacy, Scientific American (August 1992), 96-101.
3. David Chaum, Security without Identification: Transaction Systems to make Big Brother Obsolete, ACM 28 no. 10 (Oct 1985), 1030-1044.
4. David Chaum, Amos Fiat, and Moni Naor, Untraceable Electronic Cash, Advances in Cryptology CRYPTO '88, Springer-Verlag, pp. 319-327.
5. David Chaum and Torben Pedersen, Transferred Cash Grows in Size, Advances in Cryptology - EUROCRYPT '92, Springer-Verlag, pp. 390-407.
6. David Chaum and Torben Pedersen, Wallet Databases with Observers, Advances in Cryptology CRYPTO '92, Springer-Verlag, pp. 89-105.
7. Tony Eng and Tatsuaki Okamoto, Single-Term Divisible Electronic Coins, Advances in Cryptology EUROCRYPT '94, Springer-Verlag, pp. 311-33.
8. Niels Ferguson, Extensions of Single-term Coins, Advances in Cryptology - CRYPTO '93, Springer-Verlag, pp. 292-301.
9. Niels Ferguson, Single Term Off-Line Coins, Advances in Cryptology - EUROCRYPT '93, Springer-Verlag, pp. 318-328.
10. Alfred J. Menezes, Elliptic Curve Public Key Cryptosystems, Kluwer Academic Publishers, Boston, 1993.
11. Tatsuaki Okamoto, An Efficient Divisible Electronic Cash Scheme, Advances in Cryptology - CRYPTO '95, Springer-Verlag, pp. 438-451.
12. Tatsuaki Okamoto and Kazuo Ohta, Universal Electronic Cash, Advances in Cryptology - CRYPTO '91, Springer-Verlag, pp. 324-337.
13. Sebastiaan von Solms and David Naccache, On Blind Signatures and Perfect Crimes, Computers & Security 11 (1992), 581-583.
14. Markus Stadler, Jean-Marc Piveteau, and Jan Camenisch, Fair Blind Signatures, Advances in Cryptology - EUROCRYPT '95, Springer-Verlag, pp. 209-219.