The present paper focuses on one of the non-surviving preterite-present verbs, *dugan/deah ‘avail, be of use’. Although the verb exhibited a low frequency, it continued in use throughout Old and Middle English and died out only by the end of the latter period. The exception is some northern dialects and Scottish English, where it still functions as dow ‘to be able, to be willing’. The paper attempts to account for the disappearance of *dugan from English taking under consideration both language internal and external factors. The analysis covers the usage of the verb in question in Old and Middle English as well as its main and peripheral meanings. The comparison of the distribution and sense of *dugan in the two periods shows the plausible causes of its demise, which include semantic bleaching, loss of impersonal constructions from English, and the presence of the closest synonyms of *dugan.
The main goal of the paper is to show the value of texts preserved in more than one version for studies aimed at identifying reasons for the demise of words. The data selected is a set of six non-surviving English preterite-present verbs. The analysis of the material shows that mediaeval manuscripts often exhibit orthographic and morphological variation as well as differ in lexemes. Such differences prove to be useful for the search of factors leading to the elimination of the verbs in question.