Lewis Short
fĭdĕprōmissor (noun M) : fidepromitto, jurid. t. t.
* A surety, bail: pro eo, qui promittit, solent alii obligari: quorum alios sponsores, alios fidepromissores, alios fidejussores appellamus. Sponsor ita interrogatur: IDEM DARE SPONDES? fidepro missor: IDEM FIDEPROMITTIS? fidejussor ita: IDEM FIDE TVA ESSE JVBES? etc.,Gai. Inst. 3, § 115:—In another orthogr.: fidei promissor, πιστικελευστης, Gloss. Philox.
Charlton T. Lewis, Charles Short, A Latin Dictionary