bird-catching net, rare
罕 centers on scarcity: something rare or uncommon. The bird-catching net sense is a specific historical object that is itself rarely encountered, fitting the broader idea of rarity.
罕 originally depicted a net for catching birds, with the top ⺳ representing the net and 干 possibly contributing sound. The meaning 'rare' likely developed from the idea of something as uncommon as a finely made net.
The top ⺳ looks like a net spread out, and 干 below suggests a pole or frame. Picture a rare, finely crafted bird net that few people own.
For カン, imagine a rare can of bird-catching nets: can -> カン, and the can itself is a rare find.