As I understand it, it's from the 1960's, prior to the class being called Funny Car. The cars originally were called Factory Expriementals, the class suffix being AA/FX. Because little was known about chassis dynamics at the time, ride height of what was essentially a factory spec chassis, was increased, to allow larger rear tyres to sit under the backend. In addition, the general stance was altered to assist in transferring power to the rear.
The term Funny Car came about as a result, as they looked like jacked up production cars, with Kinsler injectors poking out through the bonnet. The name stuck, whilst chassis development increased and into centre driven, 125" wheelbase cars on the now familiar 17" wide slicks.