must

須 is 頁(the picture of a human head) with three strokes (or 彡) next to it, which depicts a human head with beard. In ancient China, a grown man must grow his facial hair, so 須 also has the meaning of must, then it generates 鬚, another HanZi which means beard also. In addition, both須 and 需 are the picture of beard, they have similar meanings and pronunciations, both of them may come from the same origin.