vavasour
Concise Oxford English Dictionary © 2008 Oxford University Press:
vavasour /ˈvavəsʊə/
▶noun historical a vassal owing allegiance to a great lord and having other vassals under him.
– origin ME: from OFr. vavas(s)our, from med. L. vavassor, perh. from vassus vassorum ‘vassal of vassals’.
'vavasour' also found in these Oxford entries:

