Mangled phrases

first-come, first-served

Served. The people are being served, not serving.

  • First come, first serve.

    First come, first served.

    The whole phrase is passive: the first to arrive is the first served.

The logic

Both halves describe what happens to the person: they come first, they get served first. Dropping the -d turns the second half active, which now says the first to arrive has to do the serving.

Nobody thinks that’s what it means, which is precisely why the missing D survives—the phrase still communicates perfectly. It just isn’t the phrase.

Now go put the D back.