A birth record (pre 1855) for a Canonbie Armstrong showed a place that looked like Rigg Eng does this mean anything to anybody? I can't fiind it on a map
Might be something like Rigg End (eg there's a Riggend near Airdrie). Possibly a small farm that has disappeared. You may need an old OS map to find it. Local library may help.
I have looked at an ordance map and I think the Eng must be referring to the fact that the place is in England as I have noticed a few places called Rigg just over the border in England such as Park Rigg and Prior Rigg. Does this sound feasible would someone who lived in Cumbria register their child in Scotland and visa versa?
I suspect that it is actually Rigg End, Many of the addresses in the past tended to be descriptive so an address such as Rigg End probably meant at the End of the Rigg. There are a couple of meanings for Rigg in the link below.
The Rigg-Eng almost certainly refers to England, and was the address of Walter Armstrong who had a son, Walter, on 21/10/171759. The same Walter is also recorded in the Canonbie Old Parish Record as having another son (no name) at Rigdykenook-Eng on 7/12/1761. This is very likely to be the same place. It was very common for births and baptisms from the Cumberland side of the Border to be recorded in Canonbie, especially those from Riddings and Kirkandrews-on-Esk. Bealach.