I saw the sentence "peregrinantis desideriumanobis ocasio" on an wall in a prison, and I wonder what's its meaning? I'm not sure if there's any space missing (it was hard to read).
peregrinantis desiderium a nobis oc[c]asio
Translated word by word: "of a/the traveller" "desire" "from" "us" "occasion".
This could mean several things, and it's hard to translate because the verb is missing. One would supply something like est "is", but then the placement of est can change the meaning of the sentence. It could be translated as follows: "the desire of a traveller from us is an opportunity", as in, whenever a traveller wants something from us, that is an oppportunity (for us). Even more freely, it being on a prison wall: needy pilgrims are easy to fleece.
With all due respect to our learned friends Cerberus and Brianpck, I do not think that any of the proposed translations makes the slightest bit of sense. It might be helpful to have a photograph of the graffito. In the given context one expects something like "The desire for wandering is killing us", perhaps in very inadequate Latin. "a nobis" can be compared with the use of "a" as a nota accusativi in Ibero-Romance.
Another possibility, with a slight modification of the provided text, would be:
peregrinantis desiderium a nobis oc[c]as[um].
Occasus can refer to the setting of the sun and can also be used as the participle of occido, which means "kill" or "fall." A rough translation of the above is:
The desire of a pilgrim [has been] killed by us.
Or, if we can read read "a" spatially:
The desire of a pilgrim [has] fallen away from us.
It's a speculative possibility that admits many speculative explanations. Perhaps it was an outlaw who plagued the route of a popular pilgrimage, or perhaps the inmate started as a pilgrim and then, once imprisoned, renounced his former intention.
The grammar is not correct, but I believe the intended meaning is, "We desire an opportunity to travel around." I.e., we don't want to be locked up any more. This makes perfect sense in the context of a prison.
Occasio + genitive = "an opportunity/chance of doing X"
It seems like the writer tried to use desiderium + a nobis to mean "is desired by us."
There are a couple of options to phrase this idea more grammatically in Latin. Keeping the structure of a noun clause probably requires a double dative construction: peregrinandi occasio est magno nobis desiderio.