Gosh, isn't it fascinating to read real journals from earlier times? AND--I finally found that eglwys means church; unfortunately I was unable to find anything on poor old St. Eirw--he must have been a rather minor saint.

I found this site, too, and can't resist posting rather a lot of its opening words:
It is well known that the 20th century Welsh have inherited a very restricted range of surnames. The choice is predominantly between Jones, Davies, Evans, Williams, and Thomas, not one of which is a Welsh name.

Almost certainly, the most significant factor in determining the final outcome was the persistent survival, in Wales, of the system of naming. This traditional method, common to most pastoral peoples, involved identifying a man by his father's Christian name and sometimes by his grandfather's, too. It was the practice of all the Celtic nations in Britain: the Welsh, the Scots, and the Irish. If a man's name was Cawrdaf, and he decided to call his son Dogfael, the young man would be known as Dogfael son of Cawrdaf. His son, in turn, might be Carwed son of Dogfael son of Cawrdaf.

The Welsh word for son is mab or map, depending on whether it precedes a vowel or a consonant. The Irish and Scottish word is mac. The small difference illustrates one of the main distinctions between the two surviving branches of the Celtic Language: 'q' Celtic and 'p' Celtic. Gaelic, i.e. Irish, Scottish and Manx are 'q' Celtic languages; hence Maq = Mac. Welsh, Cornish, and Breton are Brythonic, or 'p' Celtic languages, hence Map = Mab.
http://www.korrnet.org/welsh/files/jbdavies.html