A good match, perhaps from the Zürich area...

[Koen G]

Looking at the marginalia in total, the question remains if it has to be a plausible word that makes sense. I think we should focus on what we see rather than what we think words 'should' be.

There's what we see, but also what we can derive. Someone starting a word with "k" is unlikely to be writing in Latin.

What we see is k, u, and a ligature of c+3 with a macron. (I just use 3 as shorthand for the symbol).

If this were Latin, the way to read it would be kucent, which doesn't exist. Cucent doesn't either, by the way.

In German, the 3-symbol and the macron might function differently, so we need to go beyond what we can see to figure out if the word makes sense.