Of uncertain origin.
A variant form of the name Dashiell.
It became a unisex name since in 2015 actress Milla Jovovich and film director Paul W.S. Anderson named their second daughter Dashiel Edan.
Dashiell probably derives from the French surname “De Chiel”.
Sources mention an also French origin of the name, from the French surname “Deschamps”, meaning “from the fields”.
Other forms of the name are Dashiell, Dachiel, Dashel.