Etymology Apparently from Middle English *oxtere, *oxte, from Old English ōxta, ōhsta, related to Old English ōxn (“armpit”), Old English eax (“axis, axle”), and eaxl (“shoulder”), from Proto-West Germanic *ahslu (“shoulder”), from Proto-Germanic *ahslō (“joint of the shoulder”), ultimately from Proto-Indo-European *h₂eḱs- (“axis, axle”). See also axis and axon.
And begob there he was passing the door with his books under his oxter and the wife beside him and Corny Kelleher with his wall eye looking in as they went past, […]Episode 12: The Cyclops
‘It's a small beast,’ he said. ‘I could carry it under my oxter.’1955, Robin Jenkins, The Cone-Gatherers, Canongate, published 2012, page 90:
Etymology Apparently from Middle English *oxtere, *oxte, from Old English ōxta, ōhsta, related to Old English ōxn (“armpit”), Old English eax (“axis, axle”), and eaxl (“shoulder”), from Proto-West Germanic *ahslu (“shoulder”), from Proto-Germanic *ahslō (“joint of the shoulder”), ultimately from Proto-Indo-European *h₂eḱs- (“axis, axle”). See also axis and axon.
1
To hug with the arms, or support by taking the arm of.
They oxter him into the building.2022, Liam McIlvanney, The Heretic, page 412: