'mitochondrial' originates from 'mitochondrion', which comes from Greek, specifically the words 'mitos' meaning 'thread' and 'khondrion' meaning 'small granule'.

'mitochondrion' was coined in the late 19th century from Greek roots, and 'mitochondrial' was later formed as the adjective.

Initially, it referred specifically to the thread-like granules observed in cells, but over time it evolved to refer to anything related to mitochondria, the organelles responsible for energy production.