According to the Comparative Tables, the voiced labial spirant [v] developed medially both from primitive [b] and from voiceless [f] (PE19/23), which itself developed from the aspirate [pʰ]. Also according the tables, medial [v] was spelled “f”. Finally, non-initial [w] became [v] in East Danian, even in cases where it was the second part of a cluster of consonants, such as [kv] < [kw]. A [v] of this origin was spelled “v” in East Danian, and may have had a different pronunication.
References ✧ PE19/23
|ᴹ✶-khw- > -(v)||[-kʰw-] > [-xw-] > [-w-] > [-v-]||✧ PE19/23|
||✧ PE19/23 (-ph- > f = v); PE19/23 (-ph- > f = v)|
||✧ PE19/23 (-b- > -f-); PE19/23 (-b- > -f-)|
||✧ PE19/23 (-w- > -v-)|