The story
From ballpoint + pen. Compare Dutch balpen (“ballpoint pen”).
Etymology from Wiktionary, CC BY-SA 4.0.
ballpoint pen
Today it means: A pen, similar in size and shape to a pencil, having an internal chamber filled with a viscous, quick-drying ink that is dispensed at the tip during use by the rolling action of a metal sphere (around 0.7 mm to 1 mm in diameter). Full definition →