Douglas Harper's Etymology Dictionary
Rh factor
1942, from the first letters of rhesus; so called because the blood group, and its effects, were discovered in the blood of rhesus monkeys (1941).
Usage examples of "rh factor".
It was true that at the time the Rh factor had been known and in some places Rh cross matching was already in effect.
So that Miss Kellogg, who is Pa, could not have had children with a positive Rh factor from Mr.
Maybe six in every hundred have type-A blood with a negative Rh factor, but so far as we know, nobody else in this whole green world has my fingerprints.
Blood typing, Rh factor, hair and eye color, all those genetic things-you probably know more about them than I do.