Whilom
Whilom (hwī"lum) , adverb
[Anglo-Saxon hwīlum, properly, at times, dative plural of hwīl; akin to German weiland formerly, Old High German hwīlōm, See While, n.]
Formerly; once; of old; erewhile; at times. [Obsolete or Poetic] — Spenser
Whilom, as olde stories tellen us,
There was a duke that highte Theseus.