The original spelling dating from the 1500’s was “taws”, sometimes corrupted as “tawis”. The modern day spelling of “tawse” became standard in Scotland from the mid 1800’s. The use of that, the only truly accurate name, faded out around 1930 to be replaced by “the strap” and slightly later also to “the belt”, an altogether harder name. In some areas of Scotland it was also known as “the tag”, “the tash, “the lash” and “the leather”. The single most commonly used name from about 1940 to 1987 was “the belt”, and pupils knew that it was not a reference to something that held trousers up!
Yes the tawse was used quite a bit in the private school sector in Scotland up until about 1990. I attended a very strict private girls school in Glasgow and was no stranger to the McRostie.