The Roman Map of Britain Eltabo St Erth?

Eltabo (R&C 2) next

    Eltabo looks like a compound of El 'Hayle' and L. tabum 'corrupt moisture, matter'. Might tabo be used to describe a stagnant marsh, or one that was viscous? Ekwall saw Hayle as based on *Salia 'salt river', akin to Sc. seileach 'brackish'. Mills translates it as 'estuary'. I suspect Eltabo refers to the Hayle saltings as a locative element for a settlement in the vicinity of Hayle, Cornwall.
    Eltabo bears a strong resemblance to the second element of the tribal name Corieltaui. Given the common b/v confusion, perhaps Eltauo?
    Another possibility is that Eltabo is a misread Elitalio 'Hayle-brow, edge', cf. Nemetotalio and Edrotalia.
    Dilleman wrongly contended that the names beginning in El- were errors for Latin Fl. (fluvius) 'river'. PNRB adopted the position and identified  five British entries as corrupt. One, Eltavori, has since been vindicated by the careful reading of an inscribed tile. The remaining four entries, two towns and two islands, are also just that.
    Thirteenth century spellings are Heyl.

   After further consideration of the probable path of Margary 492, it seems likely that Eltabo is at a crossing of the river Hayle. St Erth SW5534 was an active port as late as the end of the 18th century. Road alignments suggest a crossing point somewhat north of the current bridge. Higher relative sea levels during the early Roman occupation may have forced the Hayle crossing further inland. 
    If he element -tabo has the IE root *tâ- 'to melt, to dissolve, to flow', then here the operative sense may be 'to melt'. The land between St Ives Bay and Mount's Bay was a major center of alluvial tin-mining, and the potential for El-tabo to indicate a smeltery (more likely a stannery) on the Hayle is intriguing.

EHNMR-625728 Roman earthwork, Roman well SW5732 (excavated by a farmer 1756)
ADS Record ID - NMR_NATINV-424959 Earthwork remains of an Iron Age or Roman round covering three acres. SW 5577 3477