Where can you find information on traditional Irish clothing?
Irish people wear no different clothing to anyone else. However Aran knitwear, which comes from a small island of the same name (the Aran Islands) creates knitwear that is distinctly Irish.
For more information, please see the related links.
The most traditional is the collection of primary information. Talk to people to find out what they think, count how many children they have, how many houses on your street. Some of this information, for larger areas and in aggregated form, may be available from official sources - but that is not really traditional. Censuses are a relatively modern innovation.