betacism

Etymology
From.

Noun

 * 1)  A sound change in which [b] (the voiced bilabial plosive) shifts to [v] (the voiced labiodental fricative).
 * Betacism is a fairly common phenomenon: it has taken place in Greek, Hebrew, Spanish, and some Portuguese dialects, among others.
 * 1) A speech disorder involving excessive use of the [b] sound, or conversion of other sounds into it.