Farenheit's "body temperature" was the axillary (armpit) temperature, and he set it to 96 degrees (on average) when creating his scale. And yes, your suppositio

Farenheit's "body temperature" was the axillary (armpit) temperature, and he set it to 96 degrees (on average) when creating his scale. And yes, your supposition about the divisibility of key numbers is right.