That may be true with regard to the Western Church only, but it has nothing at all to do with Pascha/Easter calculations, because the date of that holiday was historically set by the Church of Alexandria, according to the indigenous (Coptic) calendar which we still use. The pre-Christian Spring festival of the Egyptians (all of them, regardless of religion), Sham en-Nessim, is still a national holiday in modern Egypt, but was with the Christianization of Egypt fixed by the Church to the first Monday after Pascha, and has been kept there ever since.
So no, they weren't "blended together", and have been always very consciously and purposely kept on separate days so as to maintain that they not the same thing, though obviously the Christian observance of the same festival has been given overt Christian symbolism that isn't shared by the non-Christian population.
Why does that even slightly matter if English speakers are basically alone in calling it that? Almost everybody else (save a few oddballs in the South Slavic dialect continuum that call it "Great Day" or similar) who wasn't colonized and converted by Westerners (and several who were, like all the Spanish-speaking peoples of Latin America) calls it some variation of "Pascha". In Spanish it's Pascua, in Russian it's Paskha, in Amharic it's Fasika, in Farsi it's Eid-e Pak, etc. Even in Arabic, where its most standard name is Eid El Qiyama (lit. Festival of Resurrection), you can still call it Baskha, in imitation of Pascha. That's what we do in the Coptic Orthodox Church, in addition to using the full name.
That's a far cry from saying that they're 'pagan' in some kind of dismissive or conspiratorial fashion. We should be more like St. Justin Martyr and others in evaluating what came before our Lord's incarnation -- i.e., it is good that whatever points to truth in previous philosophies be accepted and baptized, in as far as the Church in her wisdom sees most fit. With that in mind, I'm totally fine with you all enjoying your eggs and such, but to pretend like this has corrupted the celebration of the glorious resurrection of our Lord is just lunacy. They're not even close to comparable, let alone one being the ultimate source of the other. At best, we have some cultural trappings in every place, which are likely to vary wildly. I mean, you're not celebrating Sham en-Nessim, but you don't see me or anyone in the Egyptian Church railing against a false western 'Easter' just because Sham en-Nessim was there first and they share some symbolism.
