The story of why updates are called patches is quite simple, really.
In the same way that the human being is imperfect, his creations are also imperfect. That is why, since the beginning of computing, there were bugs; errors and failures that prevent everything from working as it should.
But unlike other creations, this one could be arranged; In response to these bugs, patches, or updates, were born. Basically modifications, most of the time software but sometimes also hardware.
A little different
I speak of the time when the distinction between hardware and software was not as clear as now; when the programs are written punching holes in cards or paper tapes, which were interpreted by massive machines.
In those days, a bug could be catastrophic; Imagine feeding this machine countless cards and paper, just so that the end result is not correct. Hours, days of work spoiled, and without a simple solution.
This is how the patches were born: code modifications that the original manufacturer sent to customers for them to change the code themselves. In the package came a card or a piece of perforated tape, and an indication of the part that was wrong.
Why are updates called patches
So users had to cut the part with the error, and replace it with the new one; in some cases they even had to plug the holes that were wrong with a patch, a piece of tape.
That is the origin of the term patch; As the word indicates it is a minor fix, the term continues to be used for those small updates that don’t make a big change. They just plug the holes, literally speaking.
It is a story similar to that of the term bug, a word that was already used to define error and failure; But it was first used in computing when a moth, a bug, was found in a computer relay from 1944.