No, that's wrong, I feel. Dingsbums is more like "widget", "thingamajig", "thingummy" and many similar expressions which simply mean you're referring to something ***for which you don't know the true name*** but which has a name.
"My shoelace is coming apart and I can't stick it through the holes anymore, because I lost that plastic thingie at the end--you know, the whatchamacallit that keeps it from unravelling."
"Foobar" isn't something for which you don't know the name, on the contrary, it is an identifier such as a label in a program, for example. The label is arbitrary, and could've been something else, but they chose foobar because of it's tradition of five or more decades of use in computer contexts going back to its earliest use, probably at MIT.
So, foobar is NOT a thing which deserves no real name, but rather it is itself a name. It names something specific (and maybe important) that one is talking about in some context (often computer) and which we call by this traditionally used identifier. Each time it gets used, it may mean something different, because the identifier name is arbitrary.
One way to look at it perhaps is analogous to the way that algebraic 'x' is used--it's not that we ignore the name of 'x', 'x' is the name, because we said so, as in 'let x = [whatever]'. In the same way, 'foobar' IS the name, but 'thingummy' is not, it's just a signal that I don't know the real name.
(By the way, the shoelace thingie is an 'aglet'.)