Комментарии:Originally we related to this root Mong. beile 'prince of the 3d rank' which is usually considered to be borrowed from Manchu beile id. (cf. also Mong. beise = Man. beise 'prince of the 4th rank'). Both words are rather loans from some third language, perhaps Kitan (and cf. also the Old Bulgarian rank bojla) and may be ultimately related to PT *beg which itself is either < Chinese or < Iranian (see Шервашидзе 1989); but Mong. boji 'care' seems to be a more satisfactory comparison. Both semantically and phonetically the etymology seems quite plausible (except perhaps for the variant -i- vowel in Old Japanese, possibly conditioned by the following -j-).