Crimes of passion... Passionate love... The passion of Jesus Christ.
Anger... sexual love...suffering.
I'm trying to figure out why all these disparate states of mind can be represented by the one English word passion.
Jesus's "passion on the cross" was not sexual and probably not angry.
It turns out that the late Latin word passio comes from the classic Latin verb pati- meaning "to suffer." This meaning is related to our modern word passive--someone who is not active, who can't or doesn't take an active role in things. Being passive does seem related to suffering.
Thus the meaning we think of last--passion as suffering--was the original meaning. Good Friday is all about Jesus's passion on the cross. His suffering. This is Passion Week.
We can thank medieval Latin for giving us passionatus, meaning "full of passion" or "easily moved to passion." It's understandable how suffering evokes emotion, including anger, and thus the same word could cover both the actual suffering and the accompanying emotions.
Once passion and passionate were used to refer to overwhelming emotion in the context of suffering, I guess it wasn't a big step to include any form of "strong and barely controllable emotion" (as the Oxford American dictionary defines passion).
Sexual love is our other "barely controllable" emotion, and medieval poetry often speaks of the suffering of the lover, especially if the love is unrequited or the two lovers are separated.
Okay, I've made the stretches of meaning for passion logical, but I will still always hear the cultural meanings of passion as a faint echo behind any mention of Jesus's passion on the cross.