A good staff on the trail is why i started carrying large belt knives as a kid....so i could make a staff when i wanted one...the more uneven the terrain, the longer one needs...
The light poles are nice but when a hollow tube collapses, it does so in no halfway manner....and a bad ding seriously weakens one...and ok for poking things but useless for whacking....
The shillelagh term is actually a slang term, and actual name is a bata, which is simply a (fighting) stick or staff....just as with Robin Hood and Friar Tuck....if you want to call yours a shillelagh, then it's a shillelagh....
I suppose i should add that for any inspired by comments as to loading a stick or knob with molten lead, apart from what it does to structural integrity of smaller shafts and knobs, most readers here should be unsuprised to discover a lead loaded stick or club to be an illegal weapon in many states and localities...it ceases to be a legal cane when that is done....
As for hitting anything with a stick, the punch and jab with the end quite effective to face, ribs or hip, and generally in mine own redneck way, the buttstroke moves just to open up someone for a punch....and circular moves against arms or another stick, only to clear a path for a punch with end, or break a hold on the stick followed again with a punch...all this becomes apparent with slow motion practice...including hold breaking as you learn the leverage to tie their arms in backwards knots, and not your own.
And always remember, the greatest of all, Mr. Sherlock Holmes, was a master of one-stick fighting....as were many gentlemen of the age who trained....most old drawings which come up will show it being used in quite a few defense situations...and often using the end to keep the attacker off of you, even a larger attacker....most folk are adverse to impaling themselves...