Full Idea
Putnam argued that "water" refers to H2O by virtue of causal chains extending from present use back to early dubbing uses of it that were in fact dubbings of the substance H2O (although, of course, the original users of the word didn't know this).
Gist of Idea
Does 'water' mean a particular substance that was 'dubbed'?
Source
report of Hilary Putnam (The Meaning of 'Meaning' [1975]) by Georges Rey - Contemporary Philosophy of Mind 9.2.1
Book Reference
Rey,Georges: 'Contemporary Philosophy of Mind' [Blackwell 1997], p.242
A Reaction
This is the basic idea of the Causal Theory of Reference. Nice conclusion: most of us don't know what we are talking about. Maybe the experts on H2O are also wrong...