Because I was already taken for an (I)ncandescent Lamp, and I was used
because L (Lamp) had been assigned to Inductor a great long time ago.

Similarly, T for Transistor was taken when Joseph Henry wound the first
(T)ransformer.

These two little rascals came along relatively late in the electronics game
and there weren't a lot of letters left.

It is left as an exercise for the student to list those letters that are not
assigned to any individual component (i.e. those still available for
assignment).

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"
And what does U stand for ? Probably the stupidest choice ever aside from
Q.

Graham