falloir

to need, have to, to be necessary (that); to take (time); to be missing

“Il faut que j'y aille” — I need to go.

Inherited from Old French faloir, from an earlier falleir, from a changing of Old French faillir after its third person singular, faut, earlier falt (from Latin fallit), based off the model of valoir. Faillir derives in turn from Vulgar Latin *fallīre, from Latin fallere, fallō. Compare Franco-Provençal falêr from a similar development in Old Franco-Provençal.