Not invented here (NIH) is a stance adopted by social, corporate, or institutional cultures that avoid using or buying already existing products, research, standards, or knowledge because of their external origins and costs, such as royalties. Research illustrates a strong bias against ideas from the outside.
The reasons for not wanting to use the work of others are varied, but some can include a desire to support a local economy instead of paying royalties to a foreign license-holder, fear of patent infringement, lack of understanding of the foreign work, an unwillingness to acknowledge or value the work of others, jealousy, or forming part of a wider turf war. As a social phenomenon, this philosophy can manifest as an unwillingness to adopt an idea or product because it originates from another culture, a form of tribalism.
In programming, it is also common to refer to the "NIH syndrome" as the tendency towards reinventing the wheel (reimplementing something that is already available) based on the belief that in-house developments are inherently better suited, more secure, more controlled, quicker to develop, and incur lower overall cost (including maintenance cost) than using existing implementations.