Early golf clubs had no offset, but some club makers began experimenting with different designs, including offset, in the late 1800s. Offset gained acceptance in the 1970s, with the popularity of the Ping line of irons, all of which have featured offset hosels.
Because the clubhead is set back from the hosel and, therefore, the shaft, offset clubs help the golfer set his hands slightly ahead of the ball at address. In theory, this position squares the clubface and helps the golfer's hands lead the clubhead through impact.
Offset clubs are designed to improve the golfer's performance by helping her hit down on, rather than scoop--or hit up on--the ball and, therefore, hit the ball higher. The hosel offset also aids the golfer who slices the ball by helping close the face slightly at address.
The difference between a non-offset and an offset hosel is typically about a quarter-inch.
In the early 1990s, Cleveland designed an extreme offset iron that was dubbed the "shank-proof iron."