oblige

Concise Oxford English Dictionary © 2008 Oxford University Press:
oblige/əˈblʌɪʤ/

▶verb

• 1 (usu. be obliged to do something) make legally or morally bound to do something.

• 2 perform a service or favour for.

  ■ (be obliged) be indebted or grateful.

– derivatives
obliger noun.

– origin ME: from OFr. obliger, from L. obligare, from ob- ‘towards’ + ligare ‘to bind’.