"to drive to distraction, make crazy" (transitive), 1822; earlier in intransitive sense "to be or become mad" (1735), from mad (adj.) + -en (1). Related: Maddened; maddening. The earlier verb was simply mad (14c.), from the adjective.
<a href="https://www.etymonline.com/word/maddening">Etymology of maddening by etymonline</a>
Harper, D. (n.d.). Etymology of maddening. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/maddening