In the math/puzzle community, there are standard names for the 12 pentominos. In the order that you list them, the names are:
I ("straight 5")
L ("crooked 5")
That actually makes more sense. The straight 4 and the crooked 4 would then be the short I and short L, to continue the above convention.
The only hard part is giving up 'Utah'.
New South Wales
Buster Keaton from 'Go West'