It may represent the A.S. búte, bútu, both.
But, Bute, unless, [3017], [3616];
only, [4000].
A.S. búte.
Bute if, unless, [4059].
Buteler, butler, [2092], [2115].
Buten, about, [566].
A.S. bútan.
But-if, unless, [1713], [2698], [2949].
Buttere, butter, [1014].