also edge-ways, "with the edge turned forward or toward a particular point," 1560s, from edge (n.) + way (n.). First attested form of the word is edgewaie; the adverbial genitive -s appears by 1640s. Edgewise (1715) appears to be a variant, based on otherwise, etc. See edge (v.).
As if it were possible for any of us to slide in a word edgewise! [Mary Mitford, "Our Village," 1824].
To edge in a word in this sense is from 1680s.
1. You'll only get the desk through the door if you turn it edgeways.
2. He spent all the time talking and they could not get a word in edgeways.
3. He talks so much that no one else can get a word in edgeways.
4. He talked on and on and nobody else could get a word in edgeways.
5. If you turn it edgeways you'll get the desk through the door.