Su Jun-Ming says to Happy Web Developer
The word fork stems from the Latin word furca, meaning a "fork or similarly shaped instrument." "Fork" in the meaning of "to divide in branches, go separate ways" has been used as early as the 14th century. In the software environment, the word evokes the fork system call, which causes a running process to split itself into two (almost) identical copies that (typically) diverge to perform different tasks.