from The Century Dictionary.
- noun A weapon consisting of a sling combined with a short staff.
Sorry, no etymologies found.
And he slung a stone from his staff-sling at him so that  his head was broken thereby  and Tamon the fool was smitten lifeless where he was on the ford.
"The milch-kine and the bondwomen of the booty he shall have, and for him to hold back his staff-sling from the hosts, for not pleasant is the thunder-feat he works every evening upon them."
And he on his side shall check his staff-sling from the men of Erin and give leave to the hosts to sleep,  even though he slay them by day. "[