A little scrutiny of the tale will, I think, convince the reader that one of the objects of the original story-teller was to account for certain place-names. Thus Grugyn was meant to account for the name of Garth Grugyn, where Grugyn was killed; Gwys, to account similarly for that of Gwys, a tributary of the Twrch, which gives its name to a station on the line of railway between Ystalyfera and Bryn Amman; and Twrch Llawin to account for the name of the river Twrch, which receives the Gwys, and falls into the Tawe some distance below Ystrad Gynlais, between the counties of Brecknock and Glamorgan.
Besides Grugyn and Twrch Llawin, there was a third brother to whom the story gives a special name, to wit, Llwydawc Gouynnyat, and this was, I take it, meant also to account for a place-name, which, however, is not given: it should have been somewhere in Ystrad Yw, in the county of Brecknock. Still greater interest attaches to the swine that have not been favoured with names of their own, those referred to simply as banw, 'a young boar,' and benwic, 'a young sow.' Now banw has its equivalent in Irish in the word banbh, which O'Reilly explains as meaning a 'sucking pig,' and that is the meaning also of the Manx bannoo; but formerly the word may have had a somewhat wider meaning. The Welsh appellative is introduced twice into the story of Twrch Trwyth; once to account, as I take it, for the name Mynyd Amanw, 'Amman Mountain,' and once for Dyffryn Amanw, 'Amman Valley.' In both instances Amanw was meant, as I think, to be accounted for by the banw killed at each of the places in question. But how, you will ask, does the word banw account for Amanw, or throw any light on it at all? Very simply, if you will just suppose the name to have been Goidelic; for then you have only to provide it with the definite article and it makes in banbh, 'the pig or the boar,' and that could not in Welsh yield anything but ymmanw or ammanw [116], which with the accent shifted backwards, became Ammanw and Amman or Aman.
Having premised these explanations let us, before we proceed further, see to what our evidence exactly amounts. Here, then, we have a mention of seven swine, but as two of them, a banw and a benwic, are killed at one and the same place, our figure is practically reduced to six [117]. The question then is, in how many of these six cases the story of the hunt accounts for the names of the places of the deaths respectively, that is to say, accounts for them in the ordinary way with which one is familiar in other Welsh stories. They may be enumerated as follows:--