The process through which glossaries came into being can sometimes still be seen and studied in surviving manuscripts, and in such cases it provides a valuable index to the way in which Latin texts were studied in medieval schools. This is the case with an unprinted glossary in London, British Library, Cotton Domitian i. The glossary is mainly made up of words taken from bk III of the Bella Parisiacae urbis by Abbo of Saint-Germain-des-Prés, a work which was widely studied in English schools in the tenth and eleventh centuries, above all because of its unusual vocabulary. We know that Abbo drew the unusual vocabulary in his poem from pre-existing glossaries such as the Liber glossarum and the Scholica graecarum glossarum; but he also took from these works the interlinear glosses which he provided for the difficult words in bk III of his poem, and these in turn are found, with little variation, in all of the manuscripts which preserve the poem. Now under the rubric ‘Incipiunt glossae diversae’ in Cotton Domitian i are collected some two hundred lemmata from bk III of the poem, followed in each case by one or more glosses; on examination these glosses are found to be identical with those which accompany the text in other manuscripts. The glossary in Domitian i thus provides a working model of how a glossary was compiled, and is a further witness to the popularity of Abbo's poem in Anglo-Saxon England.