If something is fab is it wonderful, terrific, and amazingly marvellous.
If something is fabaceous, however, it's to do with beans.
It's a distinction worth bearing in mind.
Word To Use Today: fabaceous. This word comes from the Latin faba, which means bean. Fabaceous also covers things to do with peas, gorse, acacia and carob - anything with pods and nitrogen-fixing nodules on the roots.
Fab is, of course, short for fabulous. The idea is that something fab is so good it's celebrated in fables.