means Land covered with low, scrappy bushes and stunted trees rather than tall forest or open grass, typically in dry, poor, or marginal soil.

from A compound of "scrub" and "land." The key word is "scrub," which comes from the same Germanic root as "shrub" — the two are essentially the same word that drifted apart, with "scrub" coming to mean stunted, scruffy growth (and lending its name to the brushwood you scour pots with). Add the plain Old English "land" and you get exactly what it says: land full of scrub.