CURLOPT_SOCKS5_GSSAPI_SERVICE(3) on macOS

The text 4cc2b9787f3e, as macOS 10.12.5, macOS 10.12.4, macOS 10.12.3, macOS 10.12.2, macOS 10.12.1, macOS 10.12 shipped it.

SOCKS5 proxy authentication service name