The Roman Map of Britain Cutio Dolau Cothi, Carmarthenshire

Cicutio (r&c 56) next

 The form Cicutio appears to be a scribal assimilation to L. cicuta 'hemlock'. The Afon Cothi is recorded as Cothi c. 1150.

Dolau Cothi (SN6640) is the site of gold-mining and the Roman fort at Pumsaint (SN6540). Margary's Roman road 69c/62c, the Sarn Helen, connects Llanio Bremia (r&c 54), Pumsaint Alabum (r&c 55) and Dolau Cothi Cutio.

SJ2211 Guilsfield/Cegidfa *Cocito-magos
SH9775 Cegidog (St. George/Llansan siôr in Conwy)
SJ2556 Afon Cegidog 
SH6709 Afon Cadair (â-'r) Gegidan 1890
SH5041 Ystumcegid (ystum 'bend') Caernarvonshire

SH5767 Afon Cegin L. coquina 'kitchen'
SN3946 Ceginin ?

L. cicuta, W cegid, Corn kegez, Bret kegid, Br *cocit-o

Conium maculatum 'The strong association of Conium maculatum with cultivated and disturbed ground is reflected in the fact that the four records of its fossil occurrence are all from sites of Roman occupation.' Related to massive amounts of earth moved in gold-mining at Dolau Cothi? 
http://www.spookspring.com/Umbels/Hemlock.html
http://www.spookspring.com/Umbels/Cowbane.html
http://www.botanical.com/botanical/mgmh/h/hemwat19.html
http://www.botanical.com/botanical/mgmh/h/hemloc18.html   detailed history

R. J. Thomas (1938) instances of Cothi pp 134-135
Afon Cothi SN6944
Cwm-Cothi ST0998
Blaen-y-Cothy 1772 in the boundaries of Garthenor and Olmarch SN6255
Glyn Cothog in the parish of Llywel SN8730

    Thomas suggests a possible connection to the form cothi 'W bwrw allan (to eject, emit, exclude, expel)' with the prefix *eks-,W ysgothi 'to squirt, spue, purge'. This sounds like the method the Romans used to wash the gold ore from the mountainside - collecting the Afon Cothi in reservoirs, then releasing the accumulation (hydro-sluicing).
     He also suggest Corn. coth 'W hen old', Medieval Breton coth, Modern Breton cos. Perhaps this 'old' is used in the same sense as Br. sen- found in Senua (see also ERN Ennick p 148).