Shoot one’s load/wad

These slang expressions for ejaculate date from the 19th century and derive from shooting muzzle-loading firearms where loads and wadding were often fired without the ramming down of a musket ball, in which case only the wad or load was shot out. Wad also has an alternative American meaning of wad or bundle of money and to shoot one’s wad can also mean to lose all one’s money, relying of course on the context to distinguish it from the ejaculation meaning.