ocelo-durom [Ocelodurum] (toponym).
ocelom [Ocelum] (toponym).
ocelos [Ocelus] (theonym).
ocĕlos [Oclos] (anthroponym).
oc-ondĭā-ˠnos [Okondiani] (ethnonym).
oco-neʽā [Oconea] (anthroponym).
ocrās [Ocra; Okras] (oronym).
ocrĭom [Ocrium] (headland toponym).
ogĭā [Ogia] (anthroponym).
ogmiĭos [Ogmios; Ogmius] (theonym).
ogri-genos [Ogrigenus] (anthroponym).
ʽoĭ-ʽenos [Oenus] (fluvial hydronym).
ʽoĭ-istr-ʽuḃnis [Oestrymnis] (oronym).
ʽoĭ-istr-ūmnicos [Oestrymnicus] (hydronym). .
ʽoĭ-istr-ūmni-ˠdis [Oestrymnides] (insular toponym).
oll-ocos [Ollocus] (anthroponym).
ollo-dagos [Ollodagus] (theonym).
ollo-gnātos [Ollognatus] (anthroponym).
ollo-ŭodĭos [Olloudius] (theonym).
oɯbr-encās [Obrincas] (fluvial hydronym).
onnā [Onna] (toponym).
onnom [Onnum] (toponym).
onnos [Onnos] (anthroponym).
ʽon-ūɯ-aŭā [Onuaua] (theonym).
opĭ-ānos [Oppianos] (anthroponym).
orbĭo-talos [Orbiotalus] (anthroponym).
ʽorcā-ˠdis [Orcades]
ʽorcās [Orcas] (headland toponym).
ʽorcĭā [Orcia] (theonym).
ʽorcunĭā [Orcynia] (sylvan toponym).
or-eᶰ-genās [Oreginae] (toponym).
or-ʽētom [Oretum] (toponym).
orgĭ-agon [Orgiagon] (anthroponym).
or-obĭos [Orobius] (fluvial hydronym).
oro-laŭonom [Orolaunum] (toponym).
or-ʽuɯbĭos [Orobii] (ethnonym).
or-ʽumb-oŭĭos [Orumbouii] (ethnonym).
osbos [Osbus] (anthroponym).
ʽosisămĭos [Osismii] (ethnonym).
ʽosos [Osi] (ethnonym).
ʽotĭo-rīx [Otiorix] (anthroponym).
oŭi-laŭā [Ouilaua] (toponym).
oŭi-laŭis [Ouilauis] (toponym).
oŭo-ˠnĭo-rīx [Ouniorix] (theonym).
oχt-aʽĭā [Oxtaia] (anthroponym).
oχt-ap-it-arom [Octapitarum] (headland toponym).
oχt-āŭos [Oxtaus] (anthroponym).
oχto-durom [Octodurum] (toponym).