“Defendo” relates also to the phrase “charta pardonationis se defendendo”, which refers to the given pardon for murdering another person in a situation of self-defense. I.e. there should be no criminal punishment (varying in the concrete legislation).
The word relates also to the legal term “defendemus”, applicable in the Property Law. It details a request towards the vendor to protect the beneficiary of the property, against any burdens established by third parties.