it's actually "2-4-6 Heave" (for those not educated in the fine art of gun drill #1 2 4 & 6 were the numbers of the men in the gun crew detailed to heave the gun back into postion after (muzzle)loading) and would have been used during gun drill by Merchantmen; who commonly had experienced naval training. Gun drill on defensively equipped Merchant Ships would follow naval rules. 2-6 or 2-4-6 heave is a shortened variance on the call to heave by the gun captain.