(Latin). A knot or difficulty worthy of such
hands to untie. Literally, a knotty point worthy to be made a civil
action. The person who brought a civil action was called in Roman law a
vindex, and the action was called a vindicatio. If the
rightful possessor was a matter of dispute, the question became a
lis vindiciarum, and was referred to the praetor to determine. A
knotty point referred to the praetor was a “ dignus vindice nodus. ”
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894