Mac Amhalghaidh variant forms of the name. A modern variant is Mac Amhalaí. Another is Mac Amhalaidh. Another variant is Mac Amhalghadha. Variant forms of "Mac Amhalghaidh" and "Mac Amhalghadha" include Mag Amhalghaidh and Mag Amhalghadha. "Mac Amhalghaidh" translates into English as "son of "Amhalghaidh"", or "son of "Amhalghadh"". The surname originated as a patronym, however it no longer refers to the actual name of the bearer's father. The personal name "Amhalghaidh", also spelt "Amhalghadh", is an old Gaelic name, and is of uncertain origin and meaning. "Mac Amhalghaidh" is a masculine surname. The form of this surname for unmarried females is
Mac and Mc together in print two publications on filing rules, one covering that "word-by-word" convention, and another prepared in 1980 that is "letter-by-letter". A 1998 book attributes the changes to the rules to computer informatics, and notes the Mac/Mc change as its first example. 1982's "Scottish Roots", a guide for family history researchers, warns that older Scottish records do not in fact follow this convention, unlike contemporary telephone directories. A 2001 book of "New York Times" theatre reviews sorts Mc names as if spelled Mac. A 2002 official document for the State of Vermont recommends explicitly no special treatment for Mac and Mc.