Meaning – What Does ‘Killing Someone Dead’ Mean?

If used of a person, both expressions mean that he or she has left the mortal coil; the difference is in how long ago. Dead and gone always means "long dead", while dead and buried could mean that the death was recent, or it could be used as a variant of dead and gone, i.e. long dead.

If used of an object or idea, dead and gone again emphasizes that it's not just gone/obsolete/archaic/out-of-fashion, but that it has been so for a long time. With dead and buried, the emphasis is on the fact that it's out-of-date, not on how long it's been so: it might not yet be forgotten, but perhaps it ought to be.

If you disapprove of an attitude, then you'd want it "dead and buried". If you've never even heard of anyone actually believing an obsolete idea, then you could call it "dead and gone".

By itself, the expression might mean "in last place, far behind the competition," or it could simply mean, "in last place, behind all other competitors."

In this context, the word dead is used for emphasis, as if declare, "Not just near the bottom, but at the bottom."

You might ask, "Doesn't the word last imply that on its own already?" Yes, it does! However, the expression dead last is still used rather often – even if it is sometimes a tad redundant.

(Excellent question, by the way.)