- aspero (obsolete)
From Latin asperum, singular accusative of asper, from Proto-Indo-European *h₂esp- (“to cut”). The forms of the Spanish word and its Portuguese equivalent seem to indicate that they may be semi-learned or borrowed terms (the expected normal result aspro was found on rare occasions in Old Spanish documents). However, comparing it to similar cases of phonetic development in Spanish and Ibero-Romance (cf. árboles, miércoles, níspero, etc.), the preservation of the proparoxytone quality (with stress on the antepenultimate syllable) is actually normal in this word.