Why is Bill short for William?

The nickname "Bill" for William is part of a historical trend from the Middle Ages involving letter swapping and creating rhyming nicknames. Originally, the name William was shortened to "Will," and following the trend, "Will" became "Bill." This practice of creating rhyming versions of nicknames was common for many names during that period. For example, "Richard" was shortened to "Rick," which then became "Dick." The transformation from "Will" to "Bill" is also thought to be influenced by phonetic reasons, as hard consonants like "B" are easier to pronounce than soft ones like "W." This phenomenon was not unique to English; similar practices occurred in other languages and cultures as well. The nickname "Bill" has persisted over the centuries and remains a common and popular nickname for William.

For example, the full name of Bill Gates who founded Microsoft is William Henry Gates III.