What is a Murphy?

I was reading the Seattle Metro Blog and I came across this article: 'So What's a Murphy'

Have you been to Kidd Valley? Do you know of the garlic fries at the Mariner's Stadium? If that is a yes, then you know what Kidd Valley is. Apparently they call their regular fries murphies. That is such a random name, since their chili fries and garlic fries have normal names. Does anyone know the meaning behind this?