"possibly," late 15c., perhappes, with adverbial genitive, from earlier perhap (mid-14c.), from per, par "by, through" (see per) + plural of hap "chance" (see happen), on model of peradventure, perchance, etc. which now have been superseded by this word. Perhappons "possibly, by chance" is recorded from late 15c.
perhaps she will call tomorrow
perfume
perfunctory
perfuse
perfusion
pergola
perhaps
peri
peri-
perianth
pericarditis
pericardium