Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
caepa (also cēpa), ae, f., and equally freq. caepe (cēpe), is, n. (gen. caepis, Charis. p. 43 P., without voucher, but the assertion of the gram. Diom. p. 314 ib.; Prisc. p. 681 ib.; Phocae Ars, p. 1706 ib., and Serg. p. 1842 ib., that caepe is indecl., is also unsubstantiated, since the form of the gen. caepe cited by Prisc. l. l. from App. is the well-known later orthog. for caepae; v. Neue, Formenl. 1, 551; 1, 557 sq.; 1, 578; in plur. only caepae or cepae, ārum, f.; cf. Don. p. 1747 P.; Prisc. l. l.; Phoc. l. l.; Serg. l. l.; Rudd. I. p. 114, n. 36; a rare form cae-pitium, Arn. 5 init.) [etym. dub.; cf.: et capiti nomen debentia cepa, v. l. Verg. M. 74; but acc. to Charis. p. 43, from a nom. propr.], an onion; Gr. κρόμυον; cf. Plin. 19, 6, 32, § 101 sq.