Looking at the character 角, it seems impossible to guess its meaning with its current form. Let us see what we can get from its evolution history: (image taken from http://vividict.com)
Now looking at its Oracle scripts and , and especially its Bronze script , They look much like what they draw, as shown below:
|evolution history of 角|
Yes, 角 is the drawing of a horn of a buffalo or sheep.
Since 角 has sharp tip, it also used to represent something that is at a corner or with sharp tip. For example 角落.
Since angle in mathematics looks like a 角 in shape, angle is called 角 in Chinese, for example triangle is called 三角形.