Quinn comes from the Irish surname O Cuinn, often traced to a root meaning "wisdom" or "counsel" -- originally a family name long before it became a given name. As a unisex choice today, it tends to carry a sense of directness: someone whose judgment is trusted without much ceremony around it.
A Planet in an Angle doth more effectually produce his effects, but remiss in Cadent Houses. - William Lilly (1602.-1681.)