none... tartan is scottish.
Tartan
One term is lassies.
Young is indeed a Scottish surname. This is a name given to a son who had the same name as his father (similar to the "Jr" used in the USA or to the "Mac" in early Gaelic names). There is even a 'Young' tartan. It is indeed a very Scottish tradition to have your own clan tartan.
Anything - "tartan" is a pattern. Usually Scots tartan clothing is made of wool.
Generally, we think of tartan as the name for the cloth and plaid as the name for the particular pattern, but the words are often used interchangeably so that tartan can mean any checkered pattern and plaid can mean any checkered fabric. Plaid's original definition is 'as a woolen cloth having a checkered or tartan pattern'. It evolved to mean any such checkered or tartan pattern. Tartan's first definition is a 'woolen cloth woven in stripes of various colors at right angles to form a rectangular pattern; also, the pattern and design of such a cloth. Both words were first recored around the same, c.1500.
C'ainm atá ort? is used in Ulster Irish.
The form used in Irish is Heather as in English.
no Day is not a Irish last name Correct, it is not of Irish origin. Instead, it is of English origin. But Day is sometimes used for O'Dea.
Tweed and tartan.
No. It is an Irish surname used as a first name in the U.S.
As a first name it is used in both countries.
The name (from the Hebrew 'innocent lamb') is used in Ireland and even has an Irish Gaelic spelling: Réitseal, pronounced the same as the English version.