A tautology is a rhetorical figure of repetition of content, using near-synonymous morphemes, words or phrases. Colloquially, a term is used twice in succession, effectively "saying the same thing twice". In many cases, however, tautologies are based on terms or foreign words that are not understood. Good examples are:
It is precisely this abstruse and downright ridiculous form of tautology that occurs frequently in the names of caves. For some inexplicable reason, caves seem predestined for these unintentionally comical duplications. In particular, they occur with incorrect translations, where a name that already contains the word "cave" is simply regarded as a proper noun and then another "cave" is added.