In addition to Pan, mentioned in the rerun column about Satan, there are plenty of fertility figures from religions around the world with exaggerated sexual characteristics. A few examples:
– Pan’s cohorts, also pictured as semi-goats, sported horses’ portions of manhood.
– The earliest Egyptian fertility deities were always portrayed in a state of sexual arousal, though their portraits were often protected against the gazes of Victorian ladies.
– Mediterranian and African female fertility figures.
– Aztec fertility rituals around planting time involved priests masturbating on the plowed fields and their fertility deities were pictured in similar activities.
For Christian priests and missionaries, convincing their parishioners that these expressions of human fertility were not only indecent but most importantly opposed to the only god who could save them from eternal torment, and that legitimate sexual congress could only be had with the approval and through the offices of the Church, served to tighten their grip on their flock – and not only on their short and curly hairs. So it must have been natural to give the Lord of Darkness those characteristics most associated with earlier fertility deities.