electrolytic caps were actually a spin-off from another electrolytic device used in the early days of radio, called an "electrolytic rectifier". i have a book from 1917 and another book from the early 1930s showing them being used for charging batteries from an AC source. the big difference was that electrolytic rectifiers actually used aluminum plates suspended in a liquid electrolyte, and the later electrolytic caps use cardboard or paper soaked in electrolyte. most electrolytic caps still have the "rectifier" characteristic, if you forward bias the "diode" it will conduct (but it's a capacitor, and what you have actually done is reverse biased the capacitor). low reverse voltages on an electrolytic cap aren't much of a problem if they are kept to about 5% or less of the cap's rated voltage (i.e. it probably won't damage the cap, but there still might be some leakage current but not enough to damage the cap).
another obscure thing about electrolytic caps: i worked at a TV shop, and the owner had a hard time getting certain values of electrolytic caps for higher voltages (200+ volts). so he had one workbench with power supplies dedicated to "reforming" lower voltage caps to higher voltages (with a proportional reduction of the capacitance). for instance if a 10uF/400V cap was needed, a 100uf/50V cap would be connected to a 400V power supply through a 10Meg resistor, and a voltmeter would be connected across the cap. basically, this created a small leakage current through the cap, that would slowly make the oxide coating on the aluminum grow thicker until the voltage rating of the cap grew to 400V, and the meter would be reading 400V across the cap and the leakage current was less than a few microamps. this process (depending on the desired voltage rating vs the original voltage rating) could take several days. this is similar to the forming process used at the factory to form the cap when it's made (except they start with no oxide on the plates).