anesthesia

Anesthesia comes from New Latin anaesthēsia, borrowed from Ancient Greek ἀναισθησία (anaisthēsía), meaning 'without sensation.' It's formed from ἀν- (an-, 'not') plus αἴσθησις (aísthēsis, 'sensation') — literally, an- + -esthesia.

The word first appears in English in 1679 simply meaning 'insensibility,' a general lack of feeling. It wasn't until 1846 that it took on its now-familiar sense: the deliberate, medically induced state brought on by an agent.

The root aísthēsis ('sensation') is the same one buried in the idea of the 'esthetic' half of the word — both trace back to the same Greek notion of sensing or perceiving.