What is a soddy?

A soddy is the same thing as a soddie or sod house. Pioneers in the western USA built them out of the earth. See sod house for more information.

2nd Answer:
or you can just read answer #2! XD

A soddy is a dwelling having thick walls of blocks cut from an upper layer of grassland i.e,sod. Houses of this type were constructed quickly by early settlers in the Great Plains of the United States in areas where timber and stone were scarce, suitable clay was not available for making bricks in quantity, but good-quality sod was readily obtainable. Often, constructed partially underground, or built into the side of a hill to provide improved thermal insulation. The walls were usually plastered with clay to promote cleanliness and dryness within the structure, and to reduce or prevent insect infestation.
-i give all the credit for this answer to WikiWriter. i copied and pasted this answer from: http://wiki.answers.com/Q/What%20is%20a%20soddie

because it was just such a great answer!