This name, with variant spellings M(a)Crosty and M(a)cCrostie, is an Anglicized form of the Old Scottish Gaelic MacDrostan. The Gaelic prefix "mac" means "son of", plus the personal name Drostan borne by the saint to who the Abbey of Deer was dedicated. Saint Drostan is said to have lived for a time as a hermit near Glenesk in Angus and he is still commemorated there at Edgell and Lochlee. The surname is first recorded in late 16th Century Scottish records, (see below) in the form M' Rostie showing that dialectal influences have caused the initial "D" to be lost. The "ie" ending indicates the diminutive form of the name which is most widely recorded to-day in Perthshire. On December 21st 1702 Donald McCrostie and Elizabeth Stalker were married in Comrie, Perthshire and on May 22nd 1712, John son of Duncane McCrostie, was christened in Killin. On January 18th 1736 John McRosty an infant was christened in Monzievard and on January 24th 1773 John son of John McRostie and Janet Dewar, was christened in that Parish, (Perthshire). The first recorded spelling of the family name is shown to be that of Alester M'Rostie, which was dated 1585 "The Black Book of Taymouth", (Edinburgh), during the reign of King James VI of Great Britain, 1567 - 1625. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.