First come, first serve(d)

Although in the dictionary I found the phrase "first come, first served" I have often heard it pronounced
without the "d" at the end. Does anybody know whether this is only a wrong usage or where "first come, first serve" derives from (old english?).
thanks, flavia

The dictionary is correct: the "d" belongs in the phrase. Those who come first are the first to be served.

Still the version without the 'd' appears to be in common usage. A search on Altavista for the exact phrase yielded counts of

"first come first serve" 80263
"first come first served" 121214

Perhaps "first come first serve" could validly derive from something like "Those who arrive first, we serve first."(?)