Minimum acc ht of 400ft is a regulatory requirement both JAA/FAA and therefore minimum operational acceleration height is 400 ft or higher
Folks,
I would suggest the above is late in the chronology of developments.
Re. the derivation of the original 400', a most interesting piece of information, the first time I saw the results as a certification standard was SFAR 422B (B707 etc). SFAR 422B preceded the establishment of FAR 25, and a JAR was something with jam in it.
Given the T/O power time limits for such as the JT-4 (original B707-300 series), 400' fitted the time limits, with max oil temperature as well as max EGT being an issue.
The general increase to a minimum of 800' for power reduction, acceleration and configuration change was influenced, as I recall, by the loss of a South African Airways B707 departing Windhoek, Namibia.