Mid 16th century (in the sense 'enclose with stakes or pales'): from French empaler or medieval Latin impalare, from Latin in- 'in' + palus 'a stake'.

• pale from Middle English:

  The word for a ‘stake’ is from Old French pal, from Latin palus ‘stake’, which ultimately goes back to the same root found in page and pageant as well as paling (Late Middle English). The Pale was a name given to the part of Ireland under English jurisdiction before the 16th century. The earliest reference to the Pale in Ireland, from the modestly titled Introduction to Knowledge of 1547, stated that Ireland was divided into two parts, one being the English Pale and the other being ‘the wild Irish’. Many people believe that this enclosed English part of Ireland was the source of the expression beyond the pale but this is extremely unlikely, as the phrase is not recorded until the 18th century, and its origin remains something of a mystery. The Latin also gives us palisade (early 17th century), and impale (mid 16th century) first found in the sense ‘surround with a pale, fortify’, with ‘thrust a stake though’ recorded from the late 17th century. The adjective meaning ‘light’ comes via Old French pale from Latin pallidus, with the same meaning, and also the source of pallor (Late Middle English) and pallid (late 16th century), and has been in the language since the Middle Ages.