Characters
It seems to me that if there were any logic to our language, trust would be a four letter word.
— Joel Goodson ‧ Risky Business
Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker plays on English spelling to make a cynical point. If words matched their meanings, trust would be a short, blunt four-letter word like the rude ones, because it deserves the same wariness. The joke suggests trust is dangerous and best handled with suspicion.
Context reviewed