This is the 702nd most frequent Hungarian word.
fenn
"Fenn" means "up" or "above" in English.
In this sentence, 'fenn' indicates position, referring to something being up or above in the sky.
Fenn az égen ragyog a Nap.
Up in the sky, the Sun shines.
In this context, 'fenn' is used idiomatically to mean 'maintain' or 'sustain,' as applied to a non-physical concept such as hope.
Fenn kell tartanod a reményt nehéz időkben is.
You have to keep up hope even in difficult times.
Here, 'fenn' depicts the location, emphasizing that the flag is positioned at an elevated location within the tower.