Telling my family's stories
Now, I know in English that this name sounds a lot like ‘Burglar,’ but it has no relation in meaning. That’s just the unfortunate way languages work. ‘Book’ sounds almost exactly like the Turkish word for ‘shit.’ ‘Pinch’ is darn close to the f-word in Spanish. A Japanese movie called Laputa would never be shown under that title in Mexico, since it means something like ‘the whore.’ English ‘mushy’ sounds quite a bit like a German obscene term for female anatomy but a lot like the way Japanese people answer the telephone. Sound-meaning relations are typically arbitrary. Don’t make too big a deal out of it.
In German, the noun ‘berg’ means ‘mountain.’ That’s why you see it in the ends of a lot of names – Sternberg ‘Star mountain,’ Rosenberg ‘Rose mountain.’ The -ler suffix is like the -er suffix in English. ‘Someone who does x thing.’ A fisher is someone who fishes. A writer is someone who writers. In German, you add -ler to things to make them mean that kind of thing. ‘Kunst’ is ‘art.’ A ‘Künstler’ is an ‘artist’ (someone who does art).
So, a ‘Bergler’ is ‘Someone who lives in the mountains’ or a ‘mountain-dweller.’ It has nothing to do with stealing things.
There are a couple of somewhat famous Germans with this last name. Two come up readily if you search a bit:
Notably, the name Bergler is identified as a prominent Jewish name, for example in the book Jewish Family Names and their Origins: An Etymological Dictionary by Heinrich and Eva Guggenheimer identifies it as a common Jewish last name. I have no evidence for the Milwaukee Bergelers being Jewish, however.