While both Easter and Passover do follow similar rules, Passover is determine by the Jewish calendar and the equinox-- the jewish calendar is a lunar calendar-- and never quite lines up with the western calendar.
The first sunday after the first full moon was chosen to accommodate pilgrim-- who might be traveling to a major city or cathedral for Easter. Full moon's (or almost full moons) offered night time light, and made traveling safer.
there is a roman catholic tradition of visiting nine churches, and saying (reciting) the "station of the cross" on holy saturday--In time past, these might be the towns one past thru on there way to the cathedral city.
The waning moon would still be high in the sky when pilgrim started out at 4 AM, and would offer some protection from highway robbers.
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Interesting about the words for passover/easter in Spanish and Portuguese-- it very close in Italian, too. Pascali*, was a common name for boys born at eastertide. In English there is Pascal-- as in the Pascal Lamb (a name for god, and the main course for many Easter dinners!)
* I always heard it pronounced closer to Pasqualie.. But Pascali means both Passover and Easter.
