From your link:

Finally, let’s insist that the separators be part of the method name; i.e., let’s require that the name of the method be “rotate by: around:” and let’s get rid of the spaces to get “rotateby:around:” as the name and finally, let’s capitalize internal words just for readability to get “rotateBy:around:”. Then our example could be written

rotateBy: a around: v //This is Smalltalk

This is also what Objective-C / Apple does.