It is debatable whether the word, unattested in Continental French, should be spelled with a ‘u’ (vowel) or a ‘v’ (consonant). Thus the form interpreted as pitiuous would only be a variant spelling of pitus rather than a separate word. However, as the OED suggests (see etymological comment to piteous a.), the v-spelling seems to be real at least in English, and may have originated under the influence of the adjectival suffix -ive (e.g. pensive, furtive, etc.). Anglo-Norman, just like English, seems to have favoured a v-spelling too, with an entry like pitif confirming the presence of a fricative consonant.