"No estoy de humor para comer."
Translation:I am not in the mood to eat.
From Latin umor "body fluid"
In ancient and medieval physiology, "any of the four body fluids" (blood, phlegm, choler, and black bile) whose relative proportions were thought to determine state of mind. This led to a sense of "mood, temporary state of mind" (first recorded 1520s).
So, I suppose 'not in the humour for eating' would be some kind of temporary imbalance of your physical state. For example, personally, if my adrenaline was elevated, directly after a run, I would feel sick if I tried to eat, even if I was hungry.
We still use 'humour' this way In Ireland (they probably do in the UK too). In fact, if I described you as 'in good humour' it would mean in a good mood. Otherwise I would say a good 'sense of humour' to mean you are a funny person. Likewise, 'He's in a bad humour' means a bad mood... not bad jokes ;)
btw, I'm not claiming I knew the medieval physiology bit... ref: http://etymonline.com/index.php?term=humor_in_frame=0
Good info. I vaguely knew about the humors in the medieval medical sense--I studied Galen briefly in college--but since we don't use humor/humour in the US very much anymore, it's an easy connection to forget. It's always good to learn more about one's own language while studying a new one. (It's helpful with the crosswords at the very least.)