In Croatia, Trdak families are Croats (from Samobor area ). In the past century, relatively most of Croatian residents bearing this family name were born in Zagreb and Cazma.
Prevalence
About 60 people with faimily name Trdak live in Croatia today, in 30 households. There were 180 of them in the middle of the past century, and their number decreased significantly. They are located in 7 Croatian counties, four cities and 7 other places, mostly in Gornji Stupnik in Samobor area (25), Zagreb (20), in Jelovec (<10) and Konjscina (<5) in Zlatar area, and in Velika Gorica (<5).
Outside Croatia
At least one family with this surname emigrated from Croatia to the United States. Family name Trdak is present in 6 countries on three continents. "Thardak " is used by few people in the United States.
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 1906 in source Yearbook and Directory of Literary Society of St. Jerome 1906.