The name Alistair is a boy's name of Scottish, Scottish Gaelic origin meaning "defending men". Alistair is ranked #927 on our popularity charts and is often added to lists like A+ Baby Names and discussed in our forums with posts like "Pick 5 (triplets -any gender)".
From the experts:
With many British names invading the Yankee name pool, the sophisticated Alistair could and should be part of the next wave. It debuted in the US Top 1000 in 2016. You have a triple choice with this name--the British spell it Alistair or Alastair, while the Scots prefer Alasdair--but they're all suave Gaelic versions of Alexander. Adopted by the lowland Scots by the seventeenth century, the name didn't become popular outside Scotland and Ireland until the twentieth century.
Both Andrew Lloyd-Weber and Rod Stewart chose the Alastair spelling for their sons' names.