Oo

A' ae oo comes from an imaginary conversation in Scots about wool, first noted by Alan Ramsay in the glossary to his poems in 1721.

Customer ( Inquiring of the material ) : Oo? ( Wool? )
Shopkeeper : Ay oo ( Yes, it's made of wool. )
Customer : A' oo? ( All wool? )
Shopkeeper : Ay, a' oo ( Yes, all wool. )
Customer : A' ae oo? ( All the same wool? )
Shopkeeper : Ay a' ae oo ( Yes, all the same wool ).