indefatigable

indefatigable · adjective¹

1. Latin · derived fromindēfatīgābilis“untiring”
2. English todayindefatigable

From Middle French, from Latin indēfatīgābilis (“untiring”), from in- (“not”) + dēfatīgō (“to tire out”).

Indefatigable · proper noun²

Named by the British Admiralty in honor of the HMS Indefatigable.