The idea of the internal combustion engine has its roots in Huygen's design for a pump at Versailles in the 1670s.
The idea about the internal combustion engine has its roots in Huygen's design for a pump at Versailles in the 1670s.
The idea of the internal combustion engine has its roots in Huygen's design for a pump at Versailles in the 1670s.
The idea about the internal combustion engine has its roots in Huygen's design for a pump at Versailles in the 1670s.
The noun "idea" idiomatically takes the preposition "of" or a "that"-clause. It would not take "about", except in connection with verb that took "about" (such as "write"), as in "the idea about which Q wrote ..." We do not have such a verb in this example, so we need the preposition "of."