I think there is, but I don’t have a better photo. That would seem to rule out use as a pestle.
I retract my suggestion above - I viewed the image on a small screen and did not interpret it properly (I thought we were looking at a wedge with a single flute in it).
The business end of the tool looks like it’s designed for impact - splitting timber endgrain, making a distinctive mark on stone, cutting a particular type of hole in leather, impressing a mark in a workpiece to be centred/driven on a lathe, etc.
But the handle doesn’t look like it’s designed to be struck.
My grandfather used a tool sort of like that to break up apples before they went into the chipper/grinder and then into the cider press. If you put round apples in the chipper without breaking them, they’d spin and not go through. The picking baskets were smaller than a normal bucket and he’d take the tool and mash it a bunch of times into the basket and then dump it into the chipper. How much does it weigh?
It is heavy. I’m not a good judge of weight, but maybe 10-15 pounds?
My guess is it was designed to be hand-held, perhaps plunged but not struck, and the weight might be intentional or just due to the use of a common material at the time, cast iron. The nipple/point in the bottom center seems to suggest that it wasn’t used as a pestle. Or maybe that’s not the bottom, but the top? Are we sure which side is up?
It certainly looks like a star drill used by stonemasons in the manner ZenBeam described. Hit it, turn, hit it some more, and before long you have yourself a hole. There is a good example here in the 4th image from the bottom.
Except the rounded head that wouldn’t be very good for hitting.
It really is a bit of a puzzle - the weight of the iron would make this suitable for handheld use for, say, roughly chopping fruit or vegetables for animal feed - except the weight would also make that quite punishing work.
I found a not-altogether-different, although not all that similar device here, which is a turnip cutter, but that’s designed to be mounted on a wooden handle (like a spade), so as to be used standing over a bucket or barrel on the floor)
Is it for making a hole in the ground for plants? Shove it in the ground, twist to loosen the soil then insert a bulb or something?
Must say that was my immediate thought too. I came across a small stone chisel (star drill) a couple of days ago having never seen before. Except the OPs is huge and the shank is thin compared to the body.
The “thing” that is - not the OP’s personal equipment. 
A dibber? They’re always pointed.
The device resembles a lemon reamer, but it seems like cast iron would be a poor choice of material for that.
Try this guy’s blog. http://55tools.blogspot.com/
I think this will turn out to be a very specialized tool for some relatively uncommon trade. Perhaps custom made for/by one shop.
Based on the proposed uses above, I’d bet on the foundry trade - looks like something that could be used to break up molds and free a casting. It would only take a couple of strikes; so it would not be a tiring, repetitive task nor would it require a hammer. Slam it down, twist or pry and the mold is loose.
(bolding mine)
I think andyleonard and FluffyBob are correct in the sense that it’s a hand held chopper for hard fruits and vegetables.
FWIW, I’m a carpenter and have an interest in old hand tools and I’ve not come across any old woodworking tool that resembles the one linked to.
Seems awfully heavy for repetitive chopping, there are many other better designs for chopper/crushers for fruits and vegetables.
Could it have been used to break up a layer of ice in a watering trough? (Was it found in a northern climate?)
I’m not sure if it was found in Wisconsin, but the collector is in Wisconsin, and yes, I’d call it a northern climate, and brrrr. 
You might have something there. The nipple on the end, which seems to contra-indicate other uses like a pestle, would be OK for ice breaking. Maybe that would keep the tool from slipping between initial strike and further motion.
It isn’t any kind of wood gouge. The profile wouldn’t clear enough material to allow the rest of the tool to pass. And the cutting edges are in the wrong direction to form outside corners. The handle clearly indicates it’s used manually, and unlikely to be a part of something else. The point on the end would break if were used on stone, although maybe hardened would be useful with a material like brick. It’s possible this was a blacksmithing tool used to form corners by holding it place and banging the back with a mallet, but it doesn’t look any of the small number of smithing tools I’m familiar with. It seems too large and heavy for working with fruit, or as a trowel. After ruling out all other uses, I feel confident in saying that it is a piece of alien technology.
Maybe a tool for crushing ice, from back when ice was delivered in big blocks?
I couldn’t find an exact match, but the pick on the bottom of this page is similar to what I had in mind:
I can’t tell from the photo - is this tool “V” shaped?
If so, I also vote for ice chipper. Then it could also be used to shovel the ice chips.
It doesn’t look like any tool suggested so far.
It seems to have a double taper wedge. There is the top side wedge that resembles a woodworking wedge without a striking surface, attached to the bottom that also is tapered and ridged. With the leading point.
I don’t think the wedged grooves would work well as a scoop. There’s no pocket, it’s just a flat triangle groove. Nothing to catch the material on as you scoop.
I’m guessing something to do with starting a hole in the ground, maybe for planting. Weight helps get into the soil, wedge allows the soil to displace, hand tool not striking implement. Give some twist after stabbing the ground then pull out and you have a hole to stuff something into.
The ice chippers are even closer, but they all have ice pick shaped business end not wedges. 
Just to be certain about the mystery tool, the best description would be; three wedges, joined at their edges to make a three pointed one of these [sub]*[/sub] as seen from the bottom, with a handle, correct?
CMC fnord!
Who wants to change his vote to fruit crusher.