be duty bound

To be obligated or expected to do something. Now that our parents are dead, I'm duty bound to care for my siblings. As a parent, you are duty bound to protect your child.

be/feel duty/honour ˈbound to do something

(British English) (American English be/feel duty/honor ˈbound to do something) (formal) feel that you must do something because of your sense of moral duty: She felt honour bound to attend as she had promised to. ♢ Most people think that children are duty bound to look after their parents when they are old.

See also: bound, duty, feel, honour, something, to

duty bound, to be

To be firmly obligated. This term is derived from bounden duty, which dates from the 1500s and was actually redundant, since from the 1400s bound also meant “under obligations.” The term also retains this form three centuries later: “It was his bounden duty to accept the office” (Harriet Martineau, The Manchester Strike, 1833). At some point this locution was grammatically changed to the present participial usage, as in “I’m duty bound to report this violation to the dean.”