Answer
Valdas Adamkus' original surname was Adamkavičius, a patronymic surname commonly used in Lithuania during the 19th century. It was derived from his father's given name, Antanas Adamkus, with the suffix "-avičius" indicating a patronymic relationship. Adamkus later changed his surname to Adamkus, a more modern and standardized form of his original surname, which he used throughout his political career and during his presidency of Lithuania from 1998 to 2003.