pen up

verb2

1. •
   To enclose (animals) in a pen.
2. •
   To enclose as if in a pen.

   • Pent up in Utica he vainly forms / A poor Epitome of Roman Greatness, / And, cover’d with Numidian Guards, directs / A feeble Army, and an empty Senate, / Remnants of mighty Battels fought in vain. — 1712