Dic: incumbent (upon someone to do something)

• I felt it was incumbent on us all to help.
• It is incumbent on them to pay their own debts.
• It is incumbent upon all of us to make an extra effort.

Latin incumbere: to lie upon.

incumbent-: from Latin, present participle of incumbere.

Middle English, holder of an office from Medieval Latin incumbens.

adj 1. Imposed as an obligation or duty; obligatory.

adj 2. Lying, leaning, or resting on something else: incumbent rock strata.

adj 3. Currently holding a specified office: the incumbent mayor.

noun. A person who holds an office or ecclesiastical benefice: The incumbent was reelected to another term.

..... The American Heritage, Collins Essential, Cobuild