Erw (Welsh Acre)

The Welsh acre, set out in the tenth-century Laws of Hywel Dda and defined by the reach of a ploughman’s goad rather than by a day’s work.

Where the English acre was reckoned from what an ox team could plough in a day, the erw was defined dimensionally: a strip one goad-length wide and thirty long, the goad itself being a measured rod carried by the ploughman. The Laws of Hywel Dda, codified in the tenth century, build a complete land system on it, running upward through the tyddyn to the rhandir and the tref. Welsh land was still being described in erwau in estate records long after English measures had been imposed, and the word survives in Welsh place names across the country.