Give a stream of consciousness and then the final answer. Social Security is funded primarily through payroll taxes called Federal Insurance Contributions Act tax (FICA) or Self Employed Contributions Act Tax (SECA). Tax deposits are collected by the Internal Revenue Service (IRS) and are formally entrusted to the Federal Old-Age and Survivors Insurance Trust Fund and the Federal Disability Insurance Trust Fund, the two Social Security Trust Funds. With a few exceptions, all salaried income, up to an amount specifically determined by law (see tax rate table below), is subject to the Social Security payroll tax. All income over said amount is not taxed. In 2017, the maximum amount of taxable earnings was $127,200.

Based on this passage, where does the funding for social security come from?
To answer the question, consider the following: Social Security is funded primarily through payroll taxes called Federal Insurance Contributions Act tax (FICA) or Self Employed Contributions Act Tax (SECA).
So, the final answer is primarily through payroll taxes called Federal Insurance Contributions Act tax ( FICA ) or Self Employed Contributions Act Tax ( SECA ).