G'day The original names for these engines I am told is "four stroke cycle" and "two stroke cycle" - that is, the complete cycle is either two or four strokes of the piston. This has been shortened in common usage to "two stroke" and "four stroke" most commonly or two (or 2) cycle or even even shorter (by Enya for example) to 4c for "four stroke cycle" which is quite a mouth full. We just love to abbreviate things and Australians are particularly good (bad?) at it. Biscuit becomes bickie., kerosene becomes kero, metholated spirits becomes metho (denatured alcohol) and carburetor become carby. I could go on forever. We just like to shorten things. Oh yes, and Mossie for Mosquito - my all time favourite aeroplane.