The official, legal Irish version of the townland name Tobermaclugg was established in the Placenames (County Dublin) Order 2011 as Tobar na gClog “the well of the bells”. It is clear from the evidence for Tobermaclugg that the Ordnance Survey placename scholar John O’Donovan’s initial suggestion of derivation from ‘Tobar ... na g-cloch’ cannot be correct, but some historical forms do support his second suggestion, ‘Tobar ... na g-clog [Tobar na gClog]’. Interestingly, he also seems to have been aware that the earliest form of the placename may have contained a name of ecclesiastical origin, which he writes as ‘Mac Lough’. This once again demonstrates the remarkable perceptive skill of O’Donovan, as subsequent research has shown that it is doubtless the case that Tobar na gClog is a reinterpretion of an earlier placename such as *Tobar Mhac Loga which apparently contains a reference to Mic Loga “the sons of Log”, who were named among the ‘Macrad noeb hÉrenn’ “offspring of the saints of Ireland” in a text compiled over 1000 years ago (Corpus Genealogiarum Sanctorum Hiberniae, p. 156, 709 51, under the Middle Irish spelling Meic Locae). Therefore, the apparently corrupt name-form ‘Tobarmhaoilóig’ found in an Irish manuscript c.1700, might in fact represent an intermediate form between *Tobar Mhac Loga and Tobar na gClog.