The most opprobrious and vile of the back-formed singulars. It is formed from suburbs, the outskirts of a city. At first glance the process seems straightforward: if there are several suburbs, the one of them must surely be a suburb.
But, no! Suburbs is already a singular noun! It is a Latin loan word, stemming from urbs, »city«, a noun in the third declension — a schoolbook noun, one might add. The -s here is the nominative singular ending and none other; the nominative plural is urbēs. Thus, and similarly, the suburbs is »the district surrounding (literally, below) the city«, and one ought to say (for instance) that »the suburbs of London was very populous«. Unfortunately, suburbs fell victim to the simplistic scheme of articles in English and that sad, coïncidental plural S, and it has been consistently read as plural since at least the 19th century.
Sadly, any linguist worth half a damn is obliged to bend to descriptive fact: »suburb« is a real word in English. It just oughtn't be. Fortunately, the state of the thing can be changed back just as easily as it was changed: merely insist on always using it correctly and the problem will be solved — eventually. And don't pretend you have any more important concerns in your life! We here at the Institute can see all through our high-powered telescopic lenses.