Another way of saying "jerk" or "asshole", used mainly by Polish internet users.
Oh man, he behaves like a real therin.
An American individual who beats up his friend for eating his cookies and makes her barf them up. He then eats them again, barfs them back up, eats them again, barfs them back up, and cooks them in an oven. The cookies win 1st prize in a national baking contest.
Therin's cookies are so good, no wonder why they won first prize.