it's confusing even for german speakers... as i said grosses messer usually refers to a great more sabre-like weapon with a more curved blade, so optically i thought your picture was a far shorter langes messer type, but most of these categorizations are used inconsistant throughout history and our modern terms were coined/standardized by historians and antiquars. some people put both types basically in the same category but say grosses messer is basically just the larger bastard or two-handed variant of a langes messer, they aldo call it kriegsmesser or battle- or war-knife to avoid confusion.there seemingly were more and less curved and sabre-like variants in both categories... even i didn't know this and had to luck it up for clarification as the terms are often used inconsistently.well... you never stoo learning...
tolkien used long knife, big knife, great knife... hard to say what he had in mind, but recently somebody mentioned that jrrt was into historical reenactment.. i don't know if that is actually true, but if it is he might have known more about weapons and armour than we readers usually might think.
a piercing sword like the estoc could make sense against enemies like balrogs, but not agains orcs in chainmail and ringmail... i was more thinking of a fantastic sword type which combined the opportunities of several sword types rather than an estoc per se.
the sword-hammer example is intriguing... but i can't really imagine the elces fighting this style... again, against chain- and ringmailed opponents it would't make much sense...
at the moment i prefer to interprete hammer and cleaver rather as sort of kennings, than accurate descriptions.but i think we'll come up with a good solution by time...