I would hazard a guess that it is only in the last 20 to 30 years that a 27,000lb thrust engine has become known as a 27K engine? The increased use and commonality of PC's has meant that the use of K to represent 1000 has now become widespread. As for K coming from the resistor colour code that comment is slightly skewed. The resistor clolor code uses k as that is the Scientific Notation for 10*3, as Mega (M) is SN for10*6, Giga (G) 10*9and Tera (T) 10*12 etc.