The story
Either a direct clipping of Barbarian Barrel or a blend of barb (“a Barbarian: a troop in Clash Royale”) + barrel. First attested on 24 March 2018 (see quotations).
Etymology from Wiktionary, CC BY-SA 4.0.
Barbarrel
Today it means: The card Barbarian Barrel, a ground-targeting spell that does splash damage in the form of a barrel then spawns a single Barbarian troop upon reaching its destination. Full definition →