I feel that a large part of the humiur is lost in not including the fact that 笼 in mandarin means cage (笼子), and so the word latern literally means “lamp in a cage”.
Bc you know, cage…? Jail…? At least i think that’s where the joke came from? Or is OP’s dad just this random LOL
I asked my dad this and he was genuinely shocked about the connection, he hadn’t thought of it but it’s a really cool coincidence
My dad is apparently just this random LOL