'rant' originates from Low German/Dutch, specifically the word 'ranten' where 'ranten' meant 'to rave or roar.'

'rant' changed from Low German/Dutch 'ranten' and entered English usage in the late 17th century as 'rant', keeping a sense of noisy or boisterous speech.

Initially it meant 'to rave, roar or behave boisterously,' but over time it evolved into its current primary sense of 'to speak or complain loudly and angrily; a long angry speech.'