How did 'lobster' mean two different spieces?

There are many different species of lobster, but they fall into two main kinds: true (clawed) and false (spiny). CLAWED LOBSTERS - have five sets of walking legs and three sets of claws. The first set of claws is much larger than the following two sets. SPINY LOBSTERS - is the broad category for lobsters that do not have claws on the front of the body. They are instead distinguishable because of the over-sized, thick antennae that give them the ''spiny'' appearance.