Of course there are variant versions of this folk song, but I think the lyric others have speculated might be "Johnson thought that old mule had crashed through [yon back row?]" is more likely: "Johnson thought that old mule had crashed through yon CYCLONE..." And this in turn rhymes better with the next line, "You'd better bet that Johnson let that old gray mule alone." (I heard this on the 1924 recording (on You Tube) made by Gid Tanner & The Skillet Lickers. Tanner was from Georgia, which has plenty of tornadic weather.)