Reinventing the Wheel
Failing to adopt an existing solution and instead adopting or building a custom solution which performs the same function. "Reinventing the Square Wheel" refers to to the same failure, only where the solution performs worse than the existing solution.
Origin
The phrase has no single inventor. Its earliest known print appearance is in a 1956 information-science handbook, Documentation in Action, where an unnamed scientist was quoted using it to describe redundant research effort. The metaphor draws its force from the wheel's status as humanity's most archetypal foundational invention — attested in Mesopotamia by at least 3500 BCE — making the image of redesigning it from scratch a near-comic waste of intellectual effort. By the 1970s the phrase had entered general business and engineering use.