Swords to Ploughshares

Question: Why does Oko have melee as an associated ability?

Because of a neat myth that leads to his cult being strongly associated with swords! Hooray! Swords! It's on his god page, but I'll reproduce it here just for you guys.

A plague of blackbirds once descended upon the land, devouring all the crops and leaving the people starving and desperate. The birds returned every year, gobbling up all the peoples' hard work, and no arrows could harm them, nor could they be caught to stop the famine. In desperation, the people appealed to Oko for help; he then prepared a powerful medicine from secret herbs known only to him, and it drove the birds away so that the crops were saved.

The people rejoiced, but soon began to fear him, wondering if he would use the same medicine against them in turn, and though Orisha Oko gave them no sign that he would turn on them, they eventually demanded that he leave and take his frightening powers with him. No sooner had he done so, however, than the birds returned and destroyed the crops, and the chagrined people were forced to find his hut in the forest and beg him to come back, offering to make him king if he did so. He refused, disgusted by their fickleness, but granted them his sword, telling them that if they were ever in true danger, they had only to plant the sword in the ground to call upon him. He then disappeared into the earth, and the sword was kept in his shrine from that day forward.

Many shrines to Oko still contain ceremonial swords or staves (which are another important cult feature and dually symbolize fertility and, well, penises) in his honor, which are wielded ceremonially by his worshipers and those who the god chooses to ride. It's a neat connection between a god who doesn't do much in the way of fighting and the weapons and instruments of conflict with which he is nevertheless strongly connected.

Oko himself doesn't do a lot of beating people about the head with his weapons, but he had plenty of open slots for associations, and the strength of his cult attachment to such implements was good enough for us to want to represent it. He's a cool example of someone who has Melee associated without necessarily being a god of ass-whupping.