'cathodically' originates from Greek, specifically the word 'kathodos', where 'kata-' meant 'down' and 'hodos' meant 'way or path'. The English form comes via New Latin and 19th-century coinages 'cathode' + suffixes '-ic' and '-ally'.

'cathodically' changed from the adjective 'cathodic' (formed from 'cathode'), which itself was coined in the 19th century from New Latin/Greek 'kathodos' ('kathodos' → 'cathode' → 'cathodic' → 'cathodically').

Initially, the Greek root meant 'downward path'; in scientific usage from the 19th century it came to mean the electrode at which reduction occurs ('cathode'), and later adjectives/adverbs derived from it came to mean 'relating to or by means of the cathode'.