Waveband rebranding:
Prior to 1960, the millimetre wave band (to 300 GHz) was referred to as the high-frequency end of the microwave band and the terahertz region (f>300 GHz) was called the far infrared band.
Increased activities in these parts of the electromagnetic spectrum led first to the emergence of the name "millimetre wave band" for the 30-300 GHz region, and then to the name "sub-millimetre wave band" for the range 300 GHz to 3 THz.
Post year 2001 the sub-millimetre wave band started to be referred to as the terahertz band, with definitions of the upper and lower bounds of this varying widely and being author dependent. Following this, the millimetre wave band started to be referred to as the sub-terahertz band.