But you were on the right track, Doc. L. obtundo, obtundere, obtudi, obtusum (also obtunsum) 'to beat (on), thump; to stun, deafen, annoy, importune'. In traditional Latin grammar, verbs are given in four forms in the dictionary from which the rest of the verbal paradigm (or conjugation) should be recreatable: first person singular present indicative, infinitive, first person singular present perfect, and finally the neuter past particple. In the example above: 'I thump', 'to thump', 'I have thumped', 'thumped'. Same idea worked for the nominal paradigm (or declension): cite nominative singular and genitive singular, and the rest follow. (Sometimes there are exceptions, and those would be listed, too, after the four (or two) paradigmatic examples.