Hannay is a modern corruption and shortening of the old form of Ahannay, but there was an even older form, Achany or Achanny. It was derived from the Pictish Achadh-an-ath which meant "The Feilds by the Ford", and was pronounced Aha-an-any.

It has been suggested, in the alternative, that the Pictish etymon was Achadh-na-aith pronounced Aha-na-hay. This means "The Feild of the Brick Kiln". An and na both mean "of"; but when na is used it has to followed by an aspirate, Hence, na-h `aithna-hay (The name Anchenhay comes from this). As there is no trace of the survival of the last h in the forms Ahannay and Hannay, it seems pretty certain that the true derivation is rather from Achadh-an-ath, though ath is sometimes pronounced aw or awe.

De Hannethe was merely the then Norman way of rendering the name Ahannay. Eth was pronounced ay. The de was tacked on, on a mistaken idea that the name Ahannay was A`Hannay, like the Norman A`Becket and A`Kempis, -it was not-. The initial Acomes from the old Picto-Gaelic Achadh (aha)"Feild", and has no connection with the Norman"de" or "A". After Ahannay came the more modern forms Hannay, Hannah, and Hanna, but all means Achadh-an-ath. There is an English name Hanney, this may or may not be a form of the Scottish Hannay. Hanna is usually an Irish form.(H. Bruce Hannay, Judge, English High Court, Calcutta, India)