Not invented here syndrome (NIHS) is a slightly tongue-in-cheek name for the tendency of both individual developers and entire organizations to reject suitable external solutions to software development problems in favor of internally developed solutions. Closely related to the “let’s re-invent the wheel” syndrome, NIHS can be seen in intensities ranging from a mild reluctance to accept new ideas all the way up to a raging software xenophobia. NIHS can be defined as a situation where an external solution is rejected only because it was not internally developed – in other words, there are no other factors that dictate an internally developed solution would be superior. [Source: Developer.com]
Not invented here also refers to industries outside of computer programming, where organizations reject research or knowledge in favor of internally-developed solutions.