It's an easy decision to reclassify this word, so I will. In the News on the Web corpus
dooryard comes up 0.01 times per million in the United States and 0.02 times per million in Canada. In the UK and Australia it comes up zero times. And many of the US examples are from the title of the Walt Whitman poem
When Lilacs Last in the Dooryard Bloom'd, an elegy on the death of Abraham Lincoln.
To answer MK's question, no there's no possibility of the word appearing in a 9- or 10-letter puzzle.
I have to pick you up on a couple of points, MK. Your statement that, "Nine times out of ten, when playing Chi and you meet a 'common' word that you've never heard of, it will turn out to be, as in this case, North American" may be valid for those of us brought up with a British variety of English. However, from a less parochial point of view, a player from North America is likely to find that the unfamiliar "common" word turns out to be British and/or Australian.
Also, the origin of the YAWL word list is not relevant to words being common or rare. It was the original source of the complete word list, but the tagging of words as common or rare was done using other sources. As to exactly how a particular word came to be classed as common 14 years ago - that's something I'm not in a position to answer.