Anyway, the basic connection was covered above. To be more precise, Keirsey traced the temperaments through Ernst Kretschmer's Character Styles, which were divided into Cyclothymes: Hypomanic, Depressive, and Schizothymes: Anesthetic, Hyperesthetic. Cyclothymes would be Sensors and Schizothymes would be iNtuitive, and the four styles fit the asymmetrical S+J/P--N+T/F groups.
The Interaction Styles also fit the ancient temperaments, through another asymmetrical grouping: E/I +S+T/F; N+J/P.
The reason why, is that temperaments were not originally defined by perceptive (S/N) scales (Kant basically laid the foundation for that), but rather a pair of factors known as expressiveness and people/task focus. E/I fits the first one (for the Interaction Styles), and people/task is tied to T/F and J/P, but are sort of twisted by the new S/N factor.