Deafen is from deaf (Old English dēaf) plus the verb-forming suffix -en ('to make'). The base descends from Proto-Germanic *daubaz ('dull, deaf'), from a PIE root *dheubh- ('dull, obscure'). The ancestry passes through Old English dēaf, Proto-Germanic *daubaz, and Proto-Indo-European *dheubh-. In present use as a verb, it means "to make deaf or overwhelm with noise", keeping the historical formation close to the word's ordinary semantic work. Because the origin is uncertain, the safest account is descriptive: the attested senses can be explained, but the ultimate formation remains unresolved. Related words include deaf and deafness; derived forms include deafening and deafeningly.