why are they called the witches saltire?

Question

witch craft/flags

Answer 1

what are called the witches saltire?
if it helps, a saltire is a flag with a diagonal cross e.g. Scotland's flag

Answer 2

a "saltire" is an X-shaped cross, sometimes called a "St. Andrew's Cross," owing to the form of St. Andrew's traditional martyrdom.

THE Saltire is a term for the flag of Scotland, of which Andrew is the patron saint (if Presbyterians can really be said to have one ;):
The Flag of Scotland, called The Saltire or St Andrew's Cross, is a blue field with a white saltire; according to tradition, it represents Saint Andrew, who is supposed to have been crucified on a cross of that form (called a crux decussata) at Patras. The St Andrew's Cross was worn as a badge on hats in Scotland, on the day of the feast of St Andrew.[1]