
You see, it is an original use of the alphabet.
The alphabet as we know started out as pictograms as well. A for example is a turned around ox head. It later morphed into the sound βaβ as we know.
As for the rune f, it might little sense to you why it also symbolises chattel and wealth, but to my German ears it does a lot.
I will explain. The rune (letter) is read in Norse βfeβ or more originally βfehuβ. I can see the German βViehβ in it, which means cattle, livestock.
And in fact, βfeβ and βfehuβ also mean cattle and livestock.
Now you need to know that in old European cultures, the wealth of a person was measured in livestock. The Romans, for example, used sheeps, βpecusβ, as their preferred method, from which derives in the English of today the word βpecuniaryβ for money.
The same was true for the Germanic people. They also counted in livestock. That is why livestock became overtime synonymous with wealth in general.
So, it does not surprise me that the rune βfeβ was used as a placeholder for livestock and in turn wealth when they were too lazy to fully spell out. Because if you read the rune aloud, the sound itself gives it the sense it needs.
PS Reading aloud was the norm. Reading in silence was a trend of the medieval period in Europe introduced by the monks. Until then, people generally read aloud.