The tax that Jerry's grandmother and her employer paid during her working years that helped fund Social Security is called the FICA tax. FICA stands for Federal Insurance Contributions Act, and it is a payroll tax that is used to fund Social Security and Medicare. The FICA tax is split between the employer and the employee, with each paying a portion of the tax. The employee's portion of the FICA tax is deducted from their paycheck, while the employer's portion is paid separately.