deafen (v.) Look up deafen at
1590s, "to make deaf," from deaf + -en (1). The earlier verb was simply deaf (mid-15c.). For "to become deaf, to grow deaf," Old English had adeafian (intransitive), which survived into Middle English as deave but then took on a transitive sense from mid-14c. and sank from use except in dialects (where it mostly has transitive and figurative senses), leaving English without an intransitive verb here.