Extract from Northamptonshire Place Names by Charles Whynne–Hammond, published by Countryside Books, 1994.
“Here the suffix derives not from dun (hill) as might have been expected, but from denu (valley). The village stands on an upper tributary of the river Tove. The prefix is from a Saxon personal name, Helma. In the Domesday Book it was Elmedene, in 1162 Holmeden and in 1166 Helmesden.
The village grew quickly during the 19th century as a result of industrial expansion. The quarries around here supplied limestone for building large parts of Brackley and Towcester, and a rail junction linked Helmdon with Birmingham, Oxford and Northampton.
Now almost joined to the village at its southern end is Falcutt. This was Faucot in 1220 and Falcote in 1268. Fag was a Saxon word for “variegated” and usually referred to a mixture of building materials. Cote or cot was a “cottage” – obviously built with a jumble of different stones.
Nearby Stockings Farm could be corrupted from the Saxon stocc for a “stump” or “trunk”. West of Helmdon is Grange Farm which was Grounds Farm in 1823. “Grounds” was a name often used for an outlying grazing area: a pasture field away from a village.
North-eastwards towards Wappenham is Astwell, which was Estwelle in 1096 – the east wielle (spring). This is the site of a castle and 16th century fortified manor house.”