Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Lĕmannus, i, m. (with or without lacus), the Lake of Geneva.
Without lacus: deseruere cavo tentoria fixa Lemanno, Luc. 1, 396; cf. Plin. 2, 103, 106, § 224.
With lacus: Rhodanus, Lemanno lacu acceptus tenet impetum, Mel. 2, 5, 5; 2, 5, 1; Plin. 3, 4, 5, § 33; Luc. 1, 396; Mart. Cap. 6, § 635.