what does Engirth mean?

Found in the poem I Sing the Body Electric by Walt Whitman, sources suggest that 'engirth' means: to surround, to wrap, variant spelling of "engird" which means to encompass. Engird was first used in 1566.

But the problem is even the oldest dictionaries online don't have an entry for "engirth".

In the news, a dictionary of medieval Latin - described as "the most comprehensive study ever" - has finally been completed, a century after the project began. Read more at Telegraph.co.uk.