Meaning and name origin
Thaddius \th(ad)-dius\ as a boy's name is of Aramaic origin, and the meaning of Thaddius is "heart". Thaddius is a variant of Thaddeus (Aramaic): also possibly derives from Theodorus, meaning "God's gift". A given name which is rarely used.
Thaddius is not a popular first name for males and an equally uncommon surname or last name for all people (Source: 2000 U.S. Population Census).
Displayed below is a comparison of the popularity of the boy name Thaddius and its variant forms. The only popular variation form ranked in the Top 1000/100 is Thaddeus (#732). (Source: 2014 Birth Name Statistics).