Illustrated Companion to the Latin Dictionary/Fides

This article incorporates text from a publication now in the public domain: Rich, Anthony (1849). The illustrated companion to the Latin dictionary, and Greek lexicon. p. vi. OCLC 894670115. https://archive.org/details/illustratedcompa00rich. 

FIDES or FIDIS. Apparently from the Greek σφίδη, cat-gut; whence used as a general term for stringed instrument, such as the lyra, chelys, cithara. Varro, R. R. ii. 5. 12. Ov. Fast. v. 104.