Can be spelled Yarpy, Yaapie, but correctly Jaapie as it comes from the Boer -Dutch nickname for men called Jaap (just like Johnny is for John).
Although it was commonly used and perhaps still is, it isn't necessarily a kind way of naming a person because it is often used as a name for the South African equivalent of a Redneck or white right male.
Very often the term was used to describe the kind of Old Dutch males who used to be able to be spotted by their leather shorts, leather hats, full beards, thick stockings rolled over just below the knee that use elastic supports with flashes, etc. even though they were not typically backward or ignorant.
But commonly is applied to any male who is ignorant, backward, stupid and probably inbred and invariably Caucasian.
Broadly equates to the US names that are made up of two names (such as BillyBob, EllaMae, JoeBob, NormaJean, etc) and character types such as redneck, hillbilly, and inbred.