Derivational etymology implying a formal change, the loss of /r/. This is probably a secondary etymology: in the other sources depending on Orion (Meletius, Etym. Gudianum Additamenta, Etym. Magnum) we find the etymology by δράσσομαι (see δάκτυλος / δράσσομαι) without any mention of δράω. Therefore it is likely that this was the etymology in Orion, but that the abbreviator to whom we owe the main manuscript of Orion mistook δράσσω "to grasp" for δράσω, future of δράω "to accomplish", thereby creating a new etymology. It makes sense in so far as the fingers may be described as active. If the manuscript had δράσω, we could assume the explanation is the same as for the other sources, namely, that δρῶ, as the etymon of δράσσομαι, is given as etymon of δάκτυλοε, but the aorist δρᾶσαι cannot be a form of δράσσομαι, which shows that the abbreviator really meant the verb "to accomplish"