The story
The road and its name existed in the 1920s and possibly before. The road was evidently named as a route toward a place called Sand Hill, but the Sand Hill in Oakley is not the referent, as it lies in a distant part of the Bay Area. The neighborhood sense and the venture-capital industry sense are by metonymy and are many decades newer.
Etymology from Wiktionary, CC BY-SA 4.0.