A obsolete psychiatric term from the Victorian era. It comes to us from German; Grübelsucht was coined in 1876, from the German grübeln, meaning 'to brood' and sucht, meaning '-mania' or 'obsession'. It is sometimes translated into English as hair-splitting. It refers to a constant questioning and worrying over simple facts; the need to check that one put out the candle, the need to make certain that the book was placed on the table just right, the worry that the door was locked...

It was also called 'metaphysical mania' by some English speakers, and is, of course, a major component of what we today call obsessive-compulsive disorder.