what is _origin in odoo
In an onchange context it is the old value/record which was used before the change.
in odoo sale order line there is an onchange method _onchange_product_uom_qty() where they used a condition self.product_uom_qty < self._origin.product_uom_qty
Now my question is what does self._orgin is used for what does it return?
Note: 1. you can also find the origin in hr_appraisal module inside the onchange_colleagues method and somewhere in purchase 
2. I does not  mean this origin- "source document"`