'anticlactic' originates from Greek via Late Latin and English, specifically from the element 'anti-' (meaning 'against') combined with 'climax' from Greek 'klimax' (meaning 'ladder' or 'stair'), modeled on the noun 'anticlimax'.

'anticlimax' came into English from Late Latin/Greek; from that noun the adjective 'anticlimactic' developed, and 'anticlactic' emerged as a shortened/variant form of 'anticlimactic'.

Initially tied to the literal idea of a step down (opposite of a climax); over time it evolved into the figurative sense 'a disappointing or less exciting end'.