The crossword solution for the term 'Scottish Surname Starter' is MAC, which is a three-letter acronym. The acronym MAC stands for MAC or Mc, which are prefixes commonly used in Scottish surnames. The prefixes MAC and Mc are derived from the Gaelic word 'MAC, ' meaning 'son of.' This prefix is often used to indicate a patronymic surname, which is a surname derived from the name of one's father or ancestor.