"Force Majeure" was originally a civil law concept, but it is now widely used in commercial contracts, including those governed by the laws of common law jurisdictions.
Force Majeure essentially refers to events or circumstances which:
(a) are beyond the control of the contracting Parties; and
(b) make it impossible for one Party to fulfil all or a material part of its contractual obligations (i.e. they are prohibitive in nature as far as contractual performance is concerned).