Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
†† arepennis, is, m. [Gallic; in mod. Fr. arpent = an acre]; syn. with semijugerum, a half acre of ground, Col. 5, 1, 6: arapennis, Isid. Orig. 15, 15, p. 485 Lind.