[From Middle English, from Latin obtundere (to beat against), from ob-(against) + tundere (to beat). Other words derived from the same Latin root are pierce and contuse.]

Can somebody please splain me how "pierce" derives from obtundere?

Not from obtundere but from just plain ole tundere.

Well, attual® pertundere.


http://www.bartleby.com/61/46/P0294600.html

You can keep your latest ®, Faldage. It seems like an obtunded version of its ownself, and doesn't roll offf the tongue very easily.