Johnny-bag means in slang: Condom is a British term. These are most commonly made of latex. However, some can also be made with other materials like polyurethane or polyisoprene. Use it as a water balloon This can be used to have a “posh-****”. – This can be used to derogatorily cuss, e.g. “Jesus Johnny-bags”. (in Slang Dictionary, added by Ismael Blanco)