[oefnak]

Synoniemenbüch, probably?

[biztos]

Synonymwörterbuch, apparently:

https://shop.duden.de/collections/worterbucher-und-sprache/p...

[hoseja]

Synonym, of course, being latin.

[oblio]

Lazy just like us. Thesaurus in Romanian is "dicționar de sinonime". I won't bother translating it back to English, you can figure it out :-D