The name Dyllan is a variant spelling of the Welsh name Dylan, which originated from the Welsh elements "dy" meaning "great" and "llan" meaning "born." This combination suggests that the name Dylan means "great birth" or "great sailor." The name Dylan has its roots in Welsh mythology and is associated with the legendary figure Dylan Ail Don, a sea god or sea deity in Welsh folklore.

The earliest recorded use of the name Dylan dates back to the 6th century AD, where it appears in the Welsh Triads, a collection of traditional stories and legends. One of these triads mentions Dylan Ail Don as one of the three blessed youths of the Isle of Britain. The name gained popularity in Wales during the Middle Ages and was later adopted in other parts of Britain and beyond.

One of the earliest known individuals with the name Dylan was Dylan ap Gwilym, a Welsh poet who lived from around 1300 to 1370. He is considered one of the greatest poets of medieval Wales and is renowned for his cywyddau, a complex poetic form he helped popularize.

Another notable bearer of the name was Dylan Thomas, a renowned Welsh poet and writer born in 1914 and died in 1953. He is widely regarded as one of the most influential poets of the 20th century, famous for works such as "Under Milk Wood" and "Do not go gentle into that good night."

In the realm of music, Dylan Marlais Thomas, born in 1949, is a Welsh singer-songwriter and guitarist known for his contribution to the folk and folk-rock genres. He has released several albums and has been actively performing since the 1970s.

Moving to a different field, Dylan Wiliam, born in 1946, is a British educator and academic who has made significant contributions to the field of educational assessment and formative assessment practices. He is a professor emeritus at the UCL Institute of Education and has authored numerous books and articles on educational topics.

Another notable figure with the name Dylan is Dylan Alcott, an Australian paralympic tennis player and wheelchair basketball player born in 1990. He has won numerous Grand Slam titles and gold medals in both sports, and is widely regarded as one of the greatest athletes with a disability in Australian history.