I suspect that the Scotland connection is a red herring. Most of the Greeno family in Nova Scotia descend from Daniel Greeno, who was born in Ipswich, Mass and went to NS in about 1761. He had both a brother and a son named Moses. If I have your Elcony identified correctly in the 1881 census as "Elkley Greno" son of William Greno of Lakeville, Kings Co., then his father was b. ca. 1843, and with about 25 years per generation, Elcony's great great grandfather would be born somewhere in the late 1760s/early 1770s, which would be about right for Moses, son of Daniel Greeno.
Daniel's line runs back through his father Daniel and grandfather Robert to great grandfather Robert Greenough of Rowley, Mass., the first of the family to be identified.