The etymological note of the OED (songuary n. third edition, 2017) suggests that the spelling songonaire and soungnarie may be the correct resolution of the u/n confusion, with the unetymological n introduced in analogy with Latin somnus and somniaria. However, English only attests the u spelling, and the Anglo-Norman form songonaire (with what appears to be an unetymological -on addition to the root) is more easily interpreted by taking oua as a variant of ua.