The Jews of Arabia had a similar custom in pre-Islamic Arabia. This custom was part of observing the laws of “Ḥadash” (new grains). This law is described in Leviticus 23:14 “And ye shall eat neither bread, nor parched corn, nor fresh ears, until this day itself, until ye have brought the offering of your God; it is a statute for ever throughout your generations in all your dwellings.” This means that no grains — Wheat, Barley, Oat, Spelt, and Rye — could be eaten until the Omer grain offering (Arabic ‘Umra) was brought. This was done on the day after Passover. When the Temple was destroyed, the offering could no longer be brought, so new grains were forbidden to be eaten.

The prohibition of new grains was expanded to all foods including water in the first half of the third century as described in Bava Batra (60b.11): “Our Rabbis taught: When the Temple was destroyed for the second time (70 CE), large numbers in Israel became ascetics, binding themselves neither to eat meat nor to drink wine. R. Joshua got into conversation with them and said to them: My sons, why do you not eat meat nor drink wine? They replied: Shall we eat flesh which used to be brought as an offering on the altar, now that this altar is in abeyance? Shall we drink wine which used to be poured as a libation on the altar, but now no longer? He said to them: If that is so, we should not eat bread either, because the meal offerings have ceased. They said: [That is so, and] we can manage with fruit. We should not eat fruit either, [he said,] because there is no longer an offering of first-fruits. Then we can manage with other fruits [they said]. But, [he said,] we should not drink water, because there is no longer any ceremony of the pouring of water.” (Mishnah Sukkah 4)

Benjamin of Tudela mention this Jewish custom: “These Arab [Jew]s dwell in tents, and they make the desert their home. … who are the mourners of Ẓíōn and Jerusalem, and who do not eat meat nor taste wine, and sit clad in garments of black. They dwell in caves or underground houses, … and they fast forty days (Sefirat HaOmer + 10 fast days) in the year for the Jews that dwell in exile.”

The Rabbinic Jews interpreted the words “until this day itself” in the above verse (Leviticus 23:14) to mean that that new grain could be eaten after this DATE had passed even when the Temple was destroyed. The Jews of Arabia interpreted “until this day itself” to mean that grain, as well as all other foods and drink, could be eaten after the DAY had passed, so they fasted during the daytime eating only after nightfall, for the entire month of Iyyar (Ramadan) several centuries before the Hijra.

If Muharram corresponds with Tishrei, the Ramadan corresponds with Iyyar.

49 days of mourning/fasting are counted from Passover to Pentecost. The name “Pentecost” means feast of 7 weeks. The week of Passover and generally the whole month of Nisan was not included, so the main period of mourning/fasting was during Iyyar,

There are also seven weeks between Lailat al Baraat and the “6 days of fasting” in Shawal

Lastly it should be noted that although Lent is generally called quadragesima paschae (Latin for “40 days before Easter”) this was a general term. In actually it doesn’t include Sundays, which bring the total up to 46 days. Al Biruni makes the striking comment that in his day, Lent was 49 days: “Christian Lent always lasts forty-eight days, beginning on a Monday and ending on a Sunday, the forty-ninth day after its beginning.” He also calls the end of Lent, the end fasting “Eid Fitr.”

In the fourth century C.E., Christianized Rome prohibited any fasting or prostration on the days between Passover (Easter) and Pentecost, declaring them to be days of rejoicing. Anyone caught fasting or prostrating on those days would be punished: “We consider fasting as well as praying by means of prostration as unlawful on the Lord’s day (Sunday). We rejoice in the same freedom always from the day of the Pascha (Passover) to Pentecost. (Tertullian, CChr. SI., 2.1043.24-27) So I propose they moved the 49 day fast to before Easter.

In this way we can see that Sefirat HaOmer, Lent and Ramadan are all integrally related.