Why do we use informal words like "Oops!" with users when something goes wrong? What's the reason behind using this type of language during a user's interaction with a website?
As per this this article it is a derivative of the word "up a daisy". To quote this article
The Oxford English Dictionary mentions that oops is “perhaps a natural exclamation,” but some of its first appearances suggest that, along with whoops, it might derive from the phrase up-a-daisy. Up-a-daisy has been used as an utterance of nonsensical encouragement for children since the 18th century, especially upon lifting them into the air or coaxing them back on their feet after a tumble. Its first known appearance in print comes in the letters of Jonathan Swift, as “up-a-dazy,” in 1711. Over the course of the 19th century, it evolved into upsidaisy. Many of the earliest appearances of oops! and whoops! show up in the context of accidental slips and falls, suggesting that they may be related to up-a-daisy
It could also have been derived from other languages as other languages have similar words. To quote this article
Many other languages have similar expressions. An Italian found in error might say, “ops!” while a Frenchman who’s made a faux pas might say, “oups!” In Spanish, one can say opa, but just as common are huy and ¡ay! A Russian who’s made a goof might exclaim, “ой” (pronounced oj), while a German blunderer might blurt out, “hoppla!”
As per the Oxford dictionary its an natural exclamation- the sort of noises that a human being naturally makes when they might make a mistake. To quote the online Oxford dictionary site
natural exclamation: first recorded in English in the 1930s.
As noted on the Android Design Principles Writing Style page:
- Use contractions.
- Talk directly to the reader. Use “you” to refer to the reader.
- Keep your tone casual and conversational, but avoid slang.
By saying 'Oops' - in English, a commonly accepted way of acknowledging that an unexpected event has happened, in a non-frightening way - we are acknowledging a problem, but not scaring the end-user.
Compare these two error messages:
Oops! Some information wasn't complete.
Error: Please enter valid information in all required fields
Which one comes off as more friendly? Which one is less scary? Which one is more familiar? In this case, message #1. The second message is very technical (terms like 'Error', 'valid', and 'required') and very impersonal.
Additionally, it has been observed that users like language that mirrors what is used in more real-world situations. The second example is less-than-ideal because of how stilted and unnatural it is for day-to-day conversation (I'm a programmer, and even I never speak like that to other people!)
I highly recommend starting with the Android Writing Style principles, and then going and performing research against the Windows and iOS design principle documents. Surely you can gain better insight about your writing style and how it interacts with the end user.
Using informal language makes the error message more human and less intimidating. It also makes the blockage for the user less frustrating if it's language they can find humor or familiarity with. It's very much like adding a quirky illustration such as the Twitter 'fail whale' to lighten the situation. Like using "Error" or "Invalid" it is wise to add a reason for the error, and I'd suggest that language style should be consistent.
As others have said, it's an attempt to not scare the users. For example, I know someone who works at a company that writes software for devices that are used in the emergency room. One of the hospitals that uses this company's product has gotten very agitated about the application crashing. Why? In part because the application sometimes shows a message box that says Fatal error.
Imagine you're the programmer who wrote the application. You know what a fatal error is, and you don't find it alarming. It's unfortunate; it means you have to restart the application; it probably means you have a bug to fix; but it is hardly something to become agitated over.
Now imagine you are a surgeon in the operating room. You look over at one of the devices, and it is displaying Fatal error on the screen. Now, even if you are tech-savvy enough to know what this means, fatal is just not a word with good connotations. The word fatal is not well chosen for an operating room.
Rather, it would be good to have an failure message that encourages calmness. Something like "Sorry, the application has hit a glitch and needs to restart," would be less likely to alarm people who are working in a high-intensity situation.
In addition to being less intimidating, the language used in interfaces is part of a 1-on-1 conversation where you can afford to be casual, whereas language intended for a group tends to be more formal.