Desire path
The path usually represents the shortest or most easily navigated route between an origin and destination. The width and severity of erosion are often indicators of the traffic level that a path receives. Desire paths emerge as shortcuts where constructed paths take a circuitous route, have gaps, or are non-existent.
Source: Fools and their time metaphors by Aaron Z. Lewis
Desire paths or free-will ways: “paths and tracks made over time by the wishes and feet of walkers, especially those paths that run contrary to design or planning.” In other words, an unexpected behaviour that emerges as the result of poor design.