Aefauld

Simple and plain; lacking decoration, artifice, or complexity; straightforward and honest.

From Old English 'aefeld' or 'enfald' (simple, single), from 'ān' (one) plus 'fold' (fold, layer). This word comes from the same Germanic root as modern 'unfold,' but the 'ae-' prefix is Old English rather than the 'un-' we use now.