Hm. I wonder if it comes from "knight errant" - my dic. gives, as its second definition of "errant,"
2 literary or archaic travelling in search of adventure
In which case, the journey is the destination - the errand is the adventure is the errand. Or something like that.
But you're right - I don't talk about going on a journey downtown. Might say I have to make a trip downtown.
Would "object of trip/excursion" have made more sense to you?
"Excursion" seems a bit much, come to think of it....But "trip" on its own could have another meaning....
Now I see what you meant....Yes, journey is an odd word to use in the context. Frodo was on an errand to cast the one ring into the fires that made it....Calling that an errand, rather than a quest, belittles it, but he was definitely on a journey, not a trip. (Would love to see the brochures for a package tour of Mordor!)
Yes. I think you're right - a "journey" is rather too long to take place before an errand. Hum. What could they have said instead, though? Perhaps, "the object of a specific outing" or "trip"?
Ungh. I don't know!
If you can't see the bright side, polish the dull side.
