I find The Parish Register of Christ Church, Middlesex County, Va., from 1653 to 1812 that reads in part:
Sarah Trigg ye dautr of Daniell & Susannah Trigg baptz 26th of Xemb. 1686
I'm guessing that Xemb. means December, but I cannot find any source to back that up and the book has no legend for the abbreviations it uses and the adjacent entries are not chronological to give context.