Sp. dos and Eng. two
Spanish dos /ˈd̪os/ is a patrimonial descendant of Latin dŭōs ‘two’, which is the accusative, singular, masculine form of this numeral, whose nominative masculine form was dŭō. The change from Lat. dŭōs to Sp. dos is just what we would expect in a patrimonial word, for Latin short ŭ always became o in Spanish and long vowels reduced to a single one: doos > dos. Final ‑s was not lost, unlike final ‑m, which is the more common final consonant found in accusative singular words.