pai

From Old Galician-Portuguese pay < *pade, child-speech forms of padre, from Latin patrem, the accusative of pater (“father”), from Proto-Indo-European *ph₂tḗr (“father”). Doublet of padre. Compare mãe (“mother”), which underwent a similar phonetic reduction from its root (Latin mater), and, in addition, was nasalized, perhaps because it was more frequently used than this word. Cognate with Galician pai, Mirandese and Leonese pai and Aragonese pai.