The pronunciation of Stephen as Steven is a common phenomenon in English, and it can be explained by a combination of historical factors and linguistic conventions.

Firstly, it’s important to note that the name Stephen has a long and complex history. It derives from the Greek name Stephanos, which means “crown” or “garland.” The name was popularized in the early Christian era by Saint Stephen, one of the seven deacons appointed by the apostles to distribute food and aid to the poor. Saint Stephen was later stoned to death for his faith, and he is venerated as the first Christian martyr.
The name Stephen was adopted by many European languages, including Old English, where it was spelled “Stefan” or “Stefen.” However, in the Middle Ages, a new spelling emerged: “Steven.” This spelling was likely influenced by the Old French form of the name, “Estienne,” which was pronounced with a “v” sound, like “ev-tee-en.” This pronunciation was due to a phenomenon known as lenition, in which certain consonants (including “t”) become softer or even disappear altogether in certain contexts.
Over time, the “v” pronunciation of Estienne began to be applied to the English name Stephen as well. This change may have been facilitated by the fact that English had a similar sound in its language, the “v” sound. In fact, many other English words have undergone a similar sound shift, such as “bath” and “path,” which were once pronounced with a short “a” sound, but are now commonly pronounced with a long “a” sound.
So, how did this change in pronunciation become so widespread? One factor was the influence of the printing press. When the printing press was first introduced in the 15th century, there was no standardized spelling or pronunciation of English words. As a result, different printers would often spell and pronounce words differently. In the case of Stephen, it’s likely that some printers used the “v” pronunciation of the name, and this spelling became more widely accepted over time.
Another factor was the influence of dialects and regional variations. English has always had a wide range of dialects, and pronunciation can vary widely depending on where you are in the country. In some dialects, the “v” pronunciation of Stephen was more common than in others, and this may have helped to spread the pronunciation to other regions.
Finally, linguistic conventions also played a role in the adoption of the “v” pronunciation. English has a number of irregular spellings and pronunciations, and these are often the result of historical changes in the language. The fact that the spelling of Stephen remained unchanged, even as the pronunciation shifted, is an example of how language can be resistant to change. Once a spelling becomes established, it can be difficult to change, even if the pronunciation of the word has shifted significantly.
In conclusion, the pronunciation of Stephen as Steven is a result of a combination of historical, linguistic, and cultural factors. The influence of Old French, the introduction of the printing press, the influence of regional dialects, and the conventions of English spelling and pronunciation all contributed to the spread of the “v” pronunciation. Today, both pronunciations of the name are widely accepted, and it’s largely a matter of personal preference which one you use.