Meaning of W in SFPW, or a synonym that starts with a W

Question

Big disclaimer: when I was proofreading my question it sounds like I am doing a crossword puzzle. So I added some extra information to avoid confusion.

I am making an Excel sheet that assists in Risk Assessment (this particular approach of Risk Assessment is based on the RA by Bosch Rexroth as described in the book 10 Steps to Performance Level). Basically all you have to do is write a few values in certain columns and it automatically calculates the risk. The names of these columns are S, F, P, and W.

As you might have guessed, these names are singular abbreviations. I added a description tag that is visible when the column is active. The descriptions are copied from the book mentioned earlier:

S    Severity of injury          <- Makes sense
F    Frequency with duration     <- Makes sense as well
P    Possibility of avoidance    <- Same here
W    Probability of occurrence   <- What?

I can imagine that P was taken for Possibility of avoidance. But I am absolutely flabbergasted why the authors would use W as abbreviation. I can't change W to O (occurrence) because I must/am forced to copy the example sheet as described in the book. I searched around for what W could stand for, but the online acronym and abbreviation lists didn't provide an answer.

Not being able to change the abbreviation, I decided to change the description. Which would be something like:

Wrobability of occurrence

Woccurence probability

I searched around in online dictionaries and thesauri, but I couldn't find anything close.

Besides all this, I can only assume the authors had a valid reason to choose W over something more "logical" as O. It feels like I am missing the obvious.

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So in conclusion:

1. Does anyone know what the W in SFPW stands for? (SFWP is also used)

2. Or does anyone know a synonym for probability or occurrence that starts with a W?

Answer 1

W is commonly used for probability in physics. It comes, as speculated earlier, from the German language because of the high number of German physicists. For example:

http://en.wikipedia.org/wiki/Boltzmann%27s_entropy_formula

"The value of W was originally intended to be proportional to the Wahrscheinlichkeit (the German word for probability) of a macroscopic state for some probability distribution of possible microstates ..."

Answer 2

Since Bosch Rexroth sounds decidedly German, I would think that the W stands for Wahrscheinlichkeit (German for probability), which answers your first question, but doesn't really help with your second, unfortunately.