From The Seven Pillars of Wisdom by T.E. Lawrence:

Feisal, within, laboured day and night at his politics, in which so few of us could help. Outside, the crowd employed and diverted us with parades, joy-shooting, and marches of victory. Also there were accidents. Once a group, playing behind our tents, set off a seaplane bomb, dud relic of Boyle’s capture of the town. In the explosion their limbs were scattered about the camp, marking the canvas with red splashes which soon turned a dull brown and then faded pale. Feisal had the tents changed and ordered the bloody ones to be destroyed: the frugal slaves washed them. Another day a tent took fire, and part-roasted three of our guests. The camp crowded round and roared with laughter till the fire died down, and then, rather shamefacedly, we cared for their hurts. The third day, a mare was wounded by a faffing joy-bullet, and many tents were pierced

Does anyone know what a faffing joy-bullet is?