Onan in Wikipedia
In the Biblical Book of Genesis, Onan (Hebrew: אוֹנָן, Modern
Onan Tiberian ʼÔnān ; "Strong") was the second son of
Judah. Certain interpretations of the narrative concerning
him have led to the term onanism, which means coitus
According to the text, after God had killed Onan's older
brother Er, Judah told Onan to have sexual intercourse with
and impregnate Tamar, the widow of Er, so that the child or
children could be declared to be Er's heir(s). Onan had sex
with Tamar, but performed coitus interruptus each time,
spilling his "seed" (semen) on the ground, so that there would
not be any offspring which he could not claim as his own.
The passage states that this displeased God, who killed Onan
as punishment for disobedience....