 A similar Irish surname is "Mac Alastair", which translates into English as "son of "Alastar"".The Irish "Alastar" is an equivalent of the English "Alexander".Like, "Mac Alasdair", this surname no longer refers to the bearer's father, and like "Mac Alasdair" feminine forms of the name include "Nic Alastair", "Bean Mhic Alastair", and "Mhic Alastair".