Betsy Bell and Mary Gray are "twa bonnie lassies", the subject of one of the Child Ballads.
According to the ballad, Betsy and Mary were daughters of two Perthshire gentlemen, who in 1666 built themselves a bower to avoid catching a devastating plague. The girls were supplied with food by a lad in love with both of them; the lad caught the plague and gave it to them, and all three sickened and died.
Two similar hills near Omagh, County Tyrone (Northern Ireland) were named after Betsy Bell and Mary Gray by Scottish immigrants who came to Ireland to make their passage to America. There also exist twin hills in Staunton, Virginia which were also named after the girls by Scottish immigrants. Two adjacent volcanic cones in the Auckland Volcanic Field, New Zealand, (Otara Hill and Green Hill) were referred to by 19th century European settlers as Bessy Bell and Mary Gray. (See 1859 map File:AucklandMapHochstetter1859.JPG)
This article incorporates text from the public domain 1907 edition of The Nuttall Encyclopædia.