The Burning Wheel has a character Trait called "He's a Jonah, that one" (BWG p.329). Like many character Traits in BW it has no further description. So what is the trait supposed to mean?
The answer is straightforward and you found it yourself: it means a person who brings bad luck (usually to a ship). It comes from the biblical story and is an old sailor expression/superstition.
The flowery title of the trait is just a dialog example of how a NPC sailor might accuse someone of being bad luck in-game.
There's a famous movie scene about a sailor constantly accused of being a Jonah. Spoiler alert if you have never watched Master & Commander.
A good idea with BW character Traits is to look, which Lifepaths have them as Lifepath Traits. The Lifepath Crazy Old Sailor has that Trait as a LP Trait alongside Superstitious and Metal Plate in the Skull (BWG p. 190). With that it is obvious that the Trait is referring to the second source more than the first. I see three plausible ways of interpreting it:
- Other people see the character as bad luck and say "He's a Jonah, that one" about him
- The character himself is prone to labeling random people as bringers of bad luck (plays of Superstitious)
- The character was literally swallowed up by a see monster and then spat back out (where do you think the plate in his skull come from).