A "beer engine" is a device for pumping beer, originally manually operated and typically used to dispense beer from a cask or container in a pub's basement or cellar.
What is the function of a "beer engine"?
to dispense beer from a cask or container in a pub's basement or cellar

The origins of the szlachta, while ancient, have always been considered obscure.:207 As a result, its members often referred to it as odwieczna (perennial).:207 Two popular historic theories of origin forwarded by its members and earlier historians and chroniclers involved descent from the ancient Iranian tribes known as Sarmatians or from Japheth, one of Noah's sons (by contrast, the peasantry were said to be the offspring of another son of Noah, Hamand hence subject to bondage under the Curse of Hamand the Jews as the offspring of Shem). Other fanciful theories included its foundation by Julius Caesar, Alexander the Great:207 or regional leaders who had not mixed their bloodlines with those of 'slaves, prisoners, and aliens'.:208
Have the origins of the szlachta been clear or obscure?
obscure

Another solution to the problem of causality-based temporal paradoxes is that such paradoxes cannot arise simply because they have not arisen. As illustrated in numerous works of fiction, free will either ceases to exist in the past or the outcomes of such decisions are predetermined. As such, it would not be possible to enact the grandfather paradox because it is a historical fact that your grandfather was not killed before his child (your parent) was conceived. This view doesn't simply hold that history is an unchangeable constant, but that any change made by a hypothetical future time traveler would already have happened in his or her past, resulting in the reality that the traveler moves from. More elaboration on this view can be found in the Novikov self-consistency principle.
What principle elaborates more on the view described?
the Novikov self-consistency principle.