Hi, and welcome aboard
Forfill doesn't exist in the Oxford English Dictionary, and if it doesn't exist there, it means that it doesn't exist
Of course, a quick google search revealed the truth...
I have a mission to forfill for and with God.
So, I guess it's an alternative spelling for fulfill, not standardized of course (i.e. Standard AmE or BrE consider this a spelling mistake). I don't think there's any connection with religious or sexual semantic fields; just a coincidence