Lewis & Short

fĭdĕ-jŭbĕo (also separately fide ju-beo), jussi, jussum, 2, v. n. [fides], jurid. t. t., to be surety or bail, to give or go bail for any one: filiusfamilias pro patre poterit fidejubere, Dig. 46, 1, 10: servus inscio domino pro quodam fidejusserat et eo nomine pecuniam solverat, ib. 19; Ambros. de Tob. 12, 59.
Separate: fidejussores et ita interrogantur: ID FIDE TVA ESSE IVBES? Dig. 45, 1, 75, § 6; cf. Gai. Inst. 3, 115: quare scias, quodcumque ab ea ex hac causa stipulatus fueris, id me mea fide jussisse, ib. 17, 1, 60.
Pass. impers.: pro quibus fidejussum est, Dig. 46, 1, 2: qui fidejusserit, ib. 46, 3, 38 fin.