Duty Bound British American adjective formal
If you say you are duty-bound to do something, you are emphasizing that you feel it is your duty to do it.
As a teacher, you are duty-bound to teach them thoroughly.
When your parents pass away, you're duty-bound to take care of all your siblings.
He's duty-bound to submit all the documents as soon as his boss comes in.
Good morning, sir. We're duty-bound to inform you that you are arrested for deliberately killing a child.
No one made me say that, I was duty-bound to say so.
We felt duty-bound to solve the incident even though it may did harm to us.
Being looked after or protected by someone
It is used to tell someone that it is time for them to take action or make a decision.
If something falls (squarely) on someone’s shoulders, it is the responsibility that one have to take.
To give someone a particular responsibility or duty
To be + duty-bound + to do something
Sources place this idiom’s origin in the 1500s and it was actually redundant since the 1400s "bound" also meant “under obligations”. Digital records in the form of duty-bound or by duty-bound to go back to at least the 1600s. It appears as if the word is, however, started to disappear from use around the early 1900s. Over the course of the last four or five centuries, this phrase has not changed in meaning. “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 participle usage, as in “I’m duty-bound to report this violation to the dean.”