Beetle is a type of insect with wings that form a hard cover on its back when it is not flying. See it here.
It is also a heavy mallet with a large wooden head used to mash potatoes or to hammer cobblestones into place. This is how it looks.
Last but not the least, beetle also refers to anything that is jutting; overhanging: “This huge rock beetles over the edge of the town”
Betel, on the other hand, refers to a climbing pepper plant producing leaves which Asians chew (in hind, we call it pan ka patta).