Note: a quarrel may also mean an argument or fight.
A quarrel is the technical term for a crossbow bolt, so called on account of the square shape its head (from the Latin quadrus -- "a square").
(Quarrels and arrows have different characteristics. Quarrels fall at the same rate, independent of the speed of flight. Arrows, in contrast, depend on gaining lift in flight, and hence have their centre of balance at a point about 9% of their length forward of their center. This is called "point planing".)