Jenny is a diminutive form of the name Jennifer, which derives from the Welsh name Gwenhwyfar. Gwenhwyfar itself is a compound of two Welsh words - "gwen" meaning fair or white, and "hwyfar" meaning smooth or smooth voyage. The name Gwenhwyfar was a Welsh form of the name Guinevere, the legendary wife of King Arthur from Arthurian romance.

The name Gwenhwyfar first appeared in Welsh literature and mythology during the medieval period, particularly in tales of the Mabinogion and the chivalric romances of the Arthurian cycle. These stories portrayed Gwenhwyfar as a beautiful and virtuous queen, though later versions often depicted her as unfaithful to King Arthur.

The English form Jennifer emerged in the 16th century, initially as a scribal error when the name Gwenhwyfar was transcribed from Welsh to English. This error became accepted as a variant spelling, and Jennifer gradually gained popularity as a distinct name.

One of the earliest known bearers of the name Jennifer was Jennifer Carey, born in 1585, the daughter of Henry Carey, 1st Baron Hunsdon. Another early Jennifer was Jennifer Vavasor, born in 1600, who was the subject of a notorious divorce case in England.

Other notable Jennifers throughout history include:

1. Jennifer Remington (1609-1667), an English Puritan settler in Massachusetts Bay Colony.
2. Jennifer Jones (1919-2009), an American actress who won the Academy Award for Best Actress in 1943 for her performance in The Song of Bernadette.
3. Jennifer Doudna (born 1964), an American biochemist who co-discovered the CRISPR gene editing tool, for which she was awarded the 2020 Nobel Prize in Chemistry.
4. Jennifer Capriati (born 1976), an American professional tennis player and former world No. 1.
5. Jennifer Lawrence (born 1990), an American actress known for her roles in films such as The Hunger Games series and Silver Linings Playbook, for which she won the Academy Award for Best Actress in 2013.

The diminutive form Jenny emerged as a nickname for Jennifer in the 17th century and gained widespread use in the 19th and 20th centuries.