"the name - origin"
One of the most ancient cities of Greece. On the same site used to lay in the antiquity the city of Trikka (or Trikki or Trikkai), which is mentioned by Homer in the Iliad. According to mythology, it was named after nymph Trikki, daughter of the river Pinios.
The name Trikala appears after the Normans conquested the city in 1082-1083.
It is one of the few greek cities that is divided into two parts by a river (Litheos). The area of Varousi, the oldest part of the city, with the ottoman houses and the fort hovering above it is very attractive.
It's inhabitants claim that it is the most beautiful of the greek cities that are not built by the sea, but I suppose that's something up to you to decide!
here's a couple of useful links with a lot of information (the first one has A LOT of stuff, but for your inconvenience it's in greek only):