Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Bē̆thlĕhem, Bē̆thleëm, Bē̆th-lem, n. indecl., and Bē̆thlĕhēmum, i, n., = [??], a town of the tribe of Judah, the birthplace of David and of Christ, now Beit el Lahm; form Bethlehem, Tert. adv. Jud. 13; Vulg. Gen. 35, 19.
Form Bethleem, Juvenc. 1, 149; 1, 153; scanned Bĕthlēēm, Prud. στεφ. 10, 737.
Form Bethlem, Prud. Cath. 7, 1; 12, 78.
Form Bethlehemum, Hier. Vit. Paulae.
Hence,