The word gerbil is a diminutive form of  jerboa , though the jerboas are an unrelated group of rodents occupying a similar ecological niche.
A variance is a form of equitable relief that allows a property owner to bypass local zoning laws so they can use their land in the most efficient manner possible. When unusual circumstances make it difficult for a property owner to comply with local zoning laws, cities and counties may grant what are known as variances to allow property owners to circumvent the traditional zoning laws in an area.
The fixity of the real estate stock in the short-run is due to the construction lag, that is, the time needed to plan and develop a building. The construction lag is considered to be at least 6-12 months for residential and industrial, and at least 18-24 months for office and retail.