The stillest humours are always the worst.

The saying warns that apparent quietness may be read as concealing strong, troublesome emotions or intentions. Here “humours” uses an older sense: moods, temperaments, or emotional dispositions, rather than things thought funny.

It voices suspicion of hidden feeling rather than praise for open anger or passion. Because it makes a broad, potentially unfair judgment about quiet people, it should be used cautiously, not as a reliable rule of character.

Use it cautiously as an archaic observation when someone’s silence or composure seems to mask resentment, passion, or ill intent. It should not be used to stereotype quiet people or assume that calmness reveals a harmful disposition.