The mishearing that gives us 'curry favour' is of the second word. This was originally not 'favour' but 'favel'. John Palsgrave's Lesclarcissement de la langue fran�oyse [The clarification of the French language], 1530, records a curryfavell as 'a flatterar'.

Favel comes from the 1310 poem by the French royal clerk Gervais du Bus - Roman de Fauvel [The Romance of Fauvel]. That morality tale relates the story of Fauvel, an ambitious and vain donkey, who deceives and corrupts the greedy leaders of church and state. The name Fauvel or Favvel, which is formed from 'fau-vel' (in English 'veiled lie'), is an acrostic made from the initial letters of a version of the seven deadly sins: flaterie (flattery/pride), avarice (greed/gluttony), vilanie (wrath), variété (inconstancy), envie (envy), and lacheté (cowardice).

In the poem, the rich and powerful humiliate themselves by bowing down and stroking the coat of the false leader, i.e. by 'currying Fauvel'.

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