There is no good reason for the two names. Other languages refer to headed externally threaded fasteners with one name, so English ought to follow suit.
From From ISO 1891
NOTE There are differences in understanding of the distinction between the terms "bolt" and "screw" in the North American and European markets:
In the North American market a bolt is understood as an externally threaded fastener to mate with a nut and to be nut side tightened. In Europe a bolt is an externally threaded fastener with a partly threaded shank. In the North American market a screw is intended to be head side tightened and to be mounted in threaded through holes or blind holes. In Europe a screw is an externally threaded fastener with a shank threaded up to the head.
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According to Machinery's Handbook, and written by the Industrial Fasteners Institute
Differentiation between Bolt and Screw.—A bolt is an externally threaded fastener designed for insertion through holes in assembled parts, and is normally intended to be tightened or released by torquing a nut. A screw is an externally threaded fastener capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread and of being tightened or released by torquing the head. An externally threaded fastener which is prevented from being turned during assembly, and which can be tightened or released only by torquing a nut is a bolt. (Example: round head bolts, track bolts, plow bolts.) An externally threaded fastener that has a thread form which prohibits assembly with a nut having a straight thread of multiple pitch length is a screw. (Example: wood screws, tapping screws.) An externally threaded fastener that must be assembled with a nut to perform its intended service is a bolt. (Example: heavy hex structural bolt.) An externally threaded fastener that must be torqued by its head into a tapped or other preformed hole to perform its intended service is a screw. (Example: square head set screw.)
