'brain-related' originates from the combination of 'brain' and 'related', where 'brain' refers to the organ in the head responsible for thought and 'related' means connected or associated.

'brain' comes from Old English 'brægen', and 'related' comes from Latin 'relatus', the past participle of 'referre', meaning 'to bring back'.

Initially, 'brain' referred to the physical organ, and 'related' meant connected. Together, they evolved to describe anything associated with the brain.