Why is the ninth month called September?
"act or fact of guaranteeing," 1520s, garrantye, from earlier garant (see guarantee) with influence from Old French garantie "protection, defense," originally past participle of garantir "to protect," from the same source. The sense of "pledge given as security" that developed 17c. in guarantee might reasonably have left the sense "act of guaranteeing" to this form of the word, but the forms remain confused.
in law, assumption of liability for the obligations of another. In modern usage the term guaranty has largely superseded suretyship.