The story
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: To spotface from the backside of a workpiece by using a tool that passes through a through hole, deploys a cutting edge (or receives it by manual insertion from an operator), spotfaces the far side, retracts the cutting edge (or has it removed), and then retreats back through the hole (toward the tool's origin). Full definition →
Etymology from Wiktionary, CC BY-SA 4.0.