Idiom of the Day
lay down and die — To quit; to give up hope or ambition.

In British English they would probably lie down.

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I totally take back all those times I didn't want to nap when I was younger. (Anon)

I searched COCA and I got the numbers of hits as follows.
1. Lie down and die, 27
2. Lay down and die, 18

What's interesting to me is that the use of 2 is so frequent.

I would have difficulties with the explanation "that is the grammar of an average speaker". I know it would be an oversimplification, but these numbers would imply that the grammar of 40% of Americans is incorrect in this phrase.

I tried to pronounce both versions, several times. I am an ESL speaker and for me it's a bit easier to pronounce 2. I wonder if the pronunciation, the flow of speech, might contribute to the frequency of 2.

What is the opinion of English experts about this matter? Is it just the grammar of an average speaker or could there be some other factors involved?

PS

In the mean time, I run into this song refrain, which helps me to explain 2. (My emphasis added)
Lay down, lay down, lay it all down
Let your white birds smile
At the ones who stand and frown
(Melanie - Lay Down (Candles in the Rain (1970))