The KISS principle is a popular maxim often invoked when discussing design to fend off creeping featurism and control complexity of development. The traditional expansion of this acronym is "Keep it Simple, Stupid".

Maybe because of the implied irreverence (or blatant insult, depending on perception) the acronym is rarely explained. Where concerns over the word "stupid" exist, a euphemistic explanation of "Keep It Simple and Straight-forward" is sometimes resorted to. Another, gentler, explanation for the final "S" is "sweetie" as in "Keep it Simple, Sweetie." Other expansions of the acronym include "Keep it Simple and Stupid" (often used when discussing artificial intelligence), "Keep It Small and Simple", "Keep It Short and Simple" (a common marketing maxim for sales presentations) or even "Keep it Simple, Keep It Stupid", which targets to a KISKIS abbreviation.

Etymology

The "KISS" acronym is known to have been in use during the Apollo project in the 1960s. Earlier etymology of the expression is uncertain. There are several theories as to its origin:

• used as a piece of advice from lawyers counseling their clients;
• invented in the U.S. Army as army slang;
• invented at the Lockheed Skunk Works facility.

Modern usage

The KISS principle today is often used by software developers, meaning the software should be designed in the simplest way, and unneeded features should not be added. More particularly, it is a leading principle in designing critical low-level routines of operating system kernels (at least for Linux), where it suggests to write the code in the most simple and self-explaining manner, to avoid errors (or make it easy to find them). Some suggest that UNIX was invented by following the KISS principle.

The business community commonly uses the KISS principle when encouraging simpler business plans, simpler processes, and lower overhead.

See also

• Occam's Razor
• Simplicity

References