'Henge' is a modern back-formation from 'Stonehenge', Old English Stánhengist 'hanging stones'.

Separated from Stonehenge, however, it doesn't refer to the presence of trilitha, but to the general construction, an aligned ceremonial circle within a bank and ditch. Woodhenge, in Wiltshire not far from Stonehenge, and of similar age (c 2300 BCE) obviously doesn't have any surviving wood, much less lintels.

And the newly discovered wooden circle off the east coast was promptly named Seahenge.