Why are transistors called "Q"?

[David V. Corbin]

>>> Here's a question that came up at the office when a 
>>> colleague looked at a PCB and asked "why are the 
>>> transistors labelled with Q?"  Well, I suggested it might 
>>> be to avoid a clash with "T" for transformer.
>>> Or maybe "Q" represents a generic semiconductor, such as a 
>>> FET, SCR or triac.  Or is there some other reason?
>>> 

It is in one of the following three ANSI standards:

 Y1.1-1972
 Y10.5-1968
 Y10.19-1969