Penal
late Middle English: from Old French penal, from Latin poenalis, from poena ‘pain, penalty’.
wiktionary
From Old French peinal, from Medieval Latin penalis, from Latin poenalis, from poena(“punishment”), from Ancient Greek ποινή(poinḗ, “punishment”), from Proto-Indo-European *kʷoynéh₂.
etymonline
penal (adj.)
"of or pertaining to punishment by law," mid-15c., from Old French peinal (12c., Modern French pénal) and directly from Medieval Latin penalis, from Latin poenalis "pertaining to punishment," from poena "punishment," from Greek poinē "blood-money, fine, penalty, punishment," from PIE *kwoina, from root *kwei- "to pay, atone, compensate" (source also of Greek timē "price, worth, honor, esteem, respect," tinein "to pay a price, punish, take vengeance;" Sanskrit cinoti "observes, notes;" Avestan kaena "punishment, vengeance;" Old Church Slavonic cena "honor, price;" Lithuanian kaina "value, price").
