It was derived from the Miller family traditions so that when a girl and boy like each other very much they would go and engage in sexual intercourse in the wheat fields so that their parents couldn't find them. So when people asked where they were going they would respond using the code word wheat sheef.
This was first established in the 1800s when Dusty Millers daughter Michelle Lyndsay Miller was at the age of 16 and was fancying a big time kanoodle with Master Billy Baker. As Michelle and Billy were running like the wind to the wheat field they bumped into her best friend Miss Anna Warburton, and the conv went as follows:
"weeeeeeeeeeeee ye olde flangeeeaty where are you to popping off to"
"erm me and Billy were just off wheat sheefing flangeat"
"ooooooo ;) no probs see u later"
And right then and there an easy anti cock block expression was formed.
... it was a cross word answer
... private joke
... what flour to use in a seedy batch loaf
chances are he is to occpied to notice any way x