The name Gwyneth has its origins in the Welsh language and culture. It is believed to derive from the Welsh words "gwen" meaning fair or blessed, and "gwyneth" meaning happiness or joy. This combination suggests the name Gwyneth conveys a meaning of blessed happiness or fair joy.

The name dates back to at least the Middle Ages in Wales, with records showing variations like Gwenhwyvar and Gwenhwyfar used as early as the 6th century AD. These earlier forms are thought to have eventually evolved into the modern spelling of Gwyneth over time.

One of the earliest known references to the name Gwyneth appears in the medieval Welsh tales known as the Mabinogion, a collection of prose stories from the 12th-13th centuries. In these legends, the character Gwenhwyfar is depicted as a beautiful and noble woman who becomes the wife of King Arthur.

Historically, the name Gwyneth has been borne by several notable figures. One of the earliest was Gwyneth ferch Gruffydd (c. 1188–c. 1237), a Welsh princess who was the daughter of Gruffydd ap Rhys, prince of Deheubarth. Another early bearer was Gwyneth Boudler (c. 1390–c. 1430), an English woman who served as a lady-in-waiting to Queen Catherine of Valois.

In more recent times, the name Gwyneth has been carried by several famous individuals, including the acclaimed Welsh actress Gwyneth Tyson (1858–1920), known for her roles in productions of Shakespeare's plays. There is also Gwyneth King (1914–2003), a British writer and academic who authored numerous books on history and philosophy.

Perhaps the most well-known bearer of the name today is Gwyneth Paltrow (born 1972), the American actress, businesswoman, and lifestyle guru. Paltrow has won numerous awards for her film roles, including an Academy Award for Best Actress for Shakespeare in Love in 1998.