The recent terror attacks prompting a question

Today´s grisly terror attack in London had me thinking of the word
terror and its relatives in other tungues. When something like this
happens I tend to seek comfort in linguistics. What I am thinking of is
whether the swedish verb ´darra´ (shake) (old swedish the same) can
correlate and correspond to lat. tremor. The online etymology database
has the PIE base *tre- for tremor and tremble, ´shake´, and my question
is; can -t- change into -d- like this or is it grammatically
impossible? Can *tre- become swedish ´darra´?


Carl Hult