Das sehe ich auch so.

You're right. Whatnot is similar to 'what have you', implying several unnamed items--not unnamed because you don't know the names, but because the sentence has gone on long enough, or the remaining examples need not all be stated.

Whatsit / thingummie / thingummy / thingamabob / thingamajig / whatchamacallit / doodad / widget (and many similar expressions) are used when you need a placeholder for a word which escapes your memory, or you need to refer to an item whose name you don't know.

Ehhmm...cannot 'whatnot' as well be used synonymously to coll. German ".... und weiß Gott wem außerdem noch"?

ex. "And he came with his family, and grandfather, and cousins and WHATNOT"?

-gp

Das sehen Oxford Duden und Concise Oxford Dictionary aber anders. Nach ihnen ist der LEO-Eintrag richtig!

Oxford-Duden:
whatnot - A: (coll.: indefinite thing) Dingsbums, das (ugs.) B: (stand with shelves) Etagere, die
whatsit - (coll.) (thing) Dingsbums, das (ugs.); (person) Dingsda, der (ugs.)

___________

It may be the definite article 'DAS Dingsbums' that's misleading, since LEO and Oxford-Duden both use a format in which the article serves as the case marker in the dictionary listing. Oxford-Duden's note '[INDEFINITE thing]' (in contrast to 'whatsit [thing]') seems to be a muddled attempt to show that the article is not actually used in context. (@Paul: Next time could you please quote the entry you refer to? Thank you.)

I agree with Harald, minjong, Peter, and gp that 'whatnot' does not refer to a single known object (except in the sense of the piece of furniture, a translation that should be added to LEO). A helpful contrast to illustrate and confirm the point is a web search for 'and whatnot,' the normal and widespread usage, vs. 'a whatnot' or 'the whatnot', which scarcely appear except as proper names or apparent mistakes. Another way to understand it might be just to consider 'whatnot' as an indefinite pronoun, not a noun at all, similar to 'whatever,' 'anything,' 'the rest,' 'all that,' etc.

Given LEO's format constraints, it does seem that 'AND whatnot = was es sonst noch gibt' under Wendungen und Ausdrücke is clearer than 'whatnot = das Dingsbums.' So it might indeed be more helpful just to delete the latter entry, and perhaps to add another option or two for the phrase 'and whatnot' instead.

beliebt auch noch für "dingsbums" wenns um personen geht: what's-his-face:

"He came to the party with his girlfriend and, um, what's-his-face, that funny-looking guy."

Meine Anregung bezieht sich auf hms Erläuterung:

"... 'whatnot' does not refer to a single known object (except in the sense of the piece of furniture, a translation that should be added to LEO)... Another way to understand it might be just to consider 'whatnot' as an indefinite pronoun, not a noun at all, similar to 'whatever,' 'anything,' 'the rest,' 'all that,' etc."

Noch mal zu thingamajic et al: Was ich in England (selten in Amerika) oft gehoert habe ist einfach "thingy".

Platzhalter, wenn einem das richtige Wort gerade nicht einfällt