As a word, Dunum is very similar to words for fortifications and measurements, and sometimes used as a suffix or prefix in placenames to note the presence of fortification. It was a word for hill with ancient Gauls, Britons, and Saxons. It is also a latinization of the word dun, separately evolved on the continent, but to the same meaning - a fortification or a hill - in several languages, particularly Gothic. As such, variations of this placename are one of the most commonly recurring naming group for places in Ireland and an identifiable feature in placenames both in Britain and throughout much of Europe. It is similar in meaning to the Old English dün meaning down, hill or mountain and used in such English place names as Ashdown, Bredon and Snowdon.