Mǽr-þorn

According to the Old English Dictionary:

es;

mǽr-þorn

m. A hawthorn tree which serves as a boundary :-- Of ðæm pytte on ðone díc, ðæt on mǽrþorne; of ðæm þorne norþ on ðone hwítan stán, Cod. Dip. Kmbl. iii. 168, 33. mær-þorn