Early 16th century: from dad + -y².

• pope from Old English:

  The word pope came via ecclesiastical Latin from ecclesiastical Greek papas ‘bishop, patriarch’, a variant of Greek pappas ‘father’. From the same root came Late Middle English papal and papacy, and mid 16th-century papist. Patriarch (Middle English) is from Old French patriarche, via ecclesiastical Latin from Greek patriarkhēs: formed from patria ‘family’ and arkhēs ‘ruling’. Patriot (late 16th century) and patriotic (mid 17th century) go back to a related Greek patris ‘fatherland’. These are connected with English papa (late 17th century) for ‘father’ and mum, all being based on the early babbling sounds produced by infants, as is daddy (Late Middle English). See also pattern