World Book Encyclopedia (1959 Edition):
“In the A.D. 800’s the church established All Saints Day on November 1 so that the people could continue a festival they had celebrated before becoming Christians. The mass that was said on this day was called Allhallowmas. The evening before became known as All Hallow e’ven or Halloween…. It means hallowed or holy evening.”
Source and read arguments why Christians should not celebrate Halloween: http://www.letgodbetrue.com/bible/holidays/halloween.php
“That “all hallows eve” or “all saints day” is unscriptural even without the Celtic pagan additions is obvious, for (1) we have no command, precedent or example for it in the Old or New Testament; (2) the Roman Catholic holy day involved the worshiping of relics, prayers for the dead, the adoration and worship of martyrs, prayers to prominent dead saints, processions for the dead and masses for the dead; (3) in celebrating it we express a religious homage not to God who never commanded it, but to corrupt church authorities and the pope who appointed it on their own authority, which is nothing but the commandment and doctrine of man. Thus, it is not the church taking dominion over Satan’s realm, but the church playing God and acting humanistically.”
Source: “Halloween: A Biblical Critique of James Jordan and American Vision,” pages 3-4, http://www.reformedonline.com/uploads/1/5/0/3/15030584/halloween.pdf
Does the church or general assembly or pope have the authority to declare a day to be holy, or sanctified or set apart that is not authorized by the word of God? The answer to this question is no. Presbyterians are supposed to believe and teach that the church’s job is purely ministerial and that it is only to require what the Bible requires. It is only to authorize what is authorized by Scripture. Thus, the Scottish Presbyterian First Book of Discipline says, the “keeping of holy days…, all those that the papists have invented, as the feast…of Christmas [or “all hallows eve” or “all saints day”]…which things because in God’s Scriptures they neither have commandment nor assurance, we judge them utterly to be abolished from this realm.”
Source: “Halloween: A Biblical Critique of James Jordan and American Vision,” page 3, http://www.reformedonline.com/uploads/1/5/0/3/15030584/halloween.pdf
The New Westminster Directory of Liturgy and Worship on the Roman Catholic invention of All Saints Day:
“The first mention of All Saints is found in a feast commemorating the transfer of relics of martyrs from the catacombs to the Pantheon in Rome by Pope Boniface IV and the consecration of that building on 13 May 609. The date seems to have moved to 1 November after the dedication on this day of a chapel to the Savior, Mary, the apostles, martyrs and confessors in St. Peter’s. Pope Gregory III (731-41) instructed that a short office of all the saints be recited there each evening. The feast of All Martyrs and All Saints and of Our Lady was renamed the feast of All Saints in 835.”
~As quoted in Steven Wedgeworth, Halloween: Its Creation and Recreation, http://calvinistinternational.com/2013/10/30/halloween-creation-recreation/
Philip Shaff on the Roman Catholic origins of All Saints Day and All Souls Day:
“In addition to the commemoration days of particular saints, two festivals were instituted for the commemoration of all the departed.
The Festival of ALL SAINTS was introduced into the West by Pope Boniface IV. on occasion of the dedication of the Pantheon in Rome, which was originally built by Agrippa in honor of the victory of Augustus at Actium, and dedicated to Jupiter Vindex; it survived the old heathen temples, and was presented to the Pope by the Emperor Phocas, A.D. 607; whereupon it was cleansed, restored and dedicated to the service of God in the name of the ever-Virgin Mary and all martyrs. Baronius tells us that at the time of the dedication on May 13 the bones of the martyrs from the various cemeteries or in solemn procession transferred to the church in twenty-eight carriages. From Rome the festival spread during the ninth century over the West, and Gregory IV. induced Lewis the Pious in 835 to make it general in the Empire. The celebration was fixed on the first of November for the convenience of the people who after harvest had a time of leisure, and were disposed to give thanks to God for all his mercies.
The Festival of ALL SOULS is a kind of supplement it to that of All Saints, and is celebrated on the day following (Nov. 2). Its introduction is traced to Odilo, Abbot of Cluny, in the tenth century. It spread very soon without a special order, and appealed to the sympathies of that age for the sufferings of the souls in purgatory. The worshippers appear in mourning; the mass for the dead is celebrated with the “Dies irae, Dies illa,” and the oft-repeated “Requiem aeternam dona eis, Domine.” In some places (e.g. in Munich) the custom prevails of covering the graves on that day with the last flowers of the season.”
~Philip Shaff, History of the Christian Church (Grand Rapids: Eerdmans,  1987), 4:445-446.
Reed DePace on the Roman Catholic influence on modern Halloween celebrations:
“He mentions “liturgy” at one point. This reminds us that when talking about Halloween we’re not dealing with a merely secular celebration that happens to have Christian influences. We’re dealing with matters of worship. Indeed a large part of his argument to support children dressing up, getting boodles of candy, only to give dentists job security, rests of the biblical validity of the worship celebration of All Saints Day. I’ll let my puritan loose and express aghast shock at even the inference that All Saints Day has any place in the worship of the Church. My aghast sucking in of a deep breath before I blast “HOW DARE YOU!!!!???” is not opposition to remembering the martyred saints. It is opposition to introducing into worship ANYTHING that adds to God’s word, even by a set of good inferential arguments.”
Read more: https://greenbaggins.wordpress.com/2015/10/31/a-troubling-defense-of-halloween/