rabbit catching net
罘 centers on a specialized net for catching rabbits. The meaning is narrow and concrete, referring to a specific type of hunting net.
罘 combines 罒 (net) with 不, which likely contributes a phonetic element. The character specifically denotes a net for catching rabbits.
The top 罒 is a net, and the bottom 不 looks like a rabbit's long ears and body caught in it. Picture a rabbit trapped under a net.
For フ, imagine a rabbit caught in the net letting out a soft 'fu' sound of surprise: fu -> フ.