from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. petitioning, soliciting, begging, petitionary
from the GNU version of the Collaborative International Dictionary of English
- adj. Petitioning; soliciting; supplicating.
from The Century Dictionary and Cyclopedia
- Petitioning; soliciting; begging; petitionary.
- In Scots law, an action by which something is sought to be decreed by the judge in consequence of a right of property or a right of credit in the pursuer, including all actions on personal contracts by which the grantor has become bound to pay or to perform.
Sorry, no etymologies found.
Actions were petitory, when they sought to recover the very thing in controversy, or possessory, where the right of possession only was in issue.
Perhaps  another fact besides those which have been mentioned has influenced this reasoning, and that is the accurate division between possessory and petitory actions or defences in Continental procedure.