Our fathers did eat manna in the desert; as it is written, He gave them bread from heaven to eat.
Note 5 at Joh 6:31: According to Strong's Concordance, the word "manna" means literally "a whatness" and comes from the word meaning "interrogative what." The children of Israel said, "It is manna: for they wist [knew] not what it was" (Ex 16:15, brackets mine).
Manna was a nutritious food that appeared on the ground every morning beginning shortly after the children of Israel left Egypt and started their forty-year wandering in the wilderness. Moses called it "bread which the LORD hath given you to eat" (Ex 16:15). The Lord, in speaking to Moses, called it "bread from heaven" (Ex 16:4).
It was small and round, like coriander seed, and was white (Ex 16:14 with 31) or yellowish, like bdellium (Nu 11:7), in color. The people, after gathering it, ground it in mills or beat it in a mortar, baked it in pans, and made cakes of it (Nu 11:8-9). It tasted like wafers made with honey (Ex 16:31) or fresh oil (Nu 11:8). It was gathered every morning and had to be used up that day or else it stank and bred worms (Ex 16:19-20). An exception was on the sixth day; it could be gathered for the Sabbath and didn't spoil (Ex 16:22-26).
Moses was commanded by God to keep an omer (or half gallon) of it as a memorial of God's provision in the wilderness (Ex 16:32-35). In spite of this obvious heavenly provision from God, the children of Israel grew tired of a steady diet of manna and began murmuring and complaining (Nu 11:4-6), which angered the Lord and Moses (Nu 11:10).
The manna did not cease until the day after the children of Israel crossed the Jordan and entered the Promised Land (Jos 5:10-12). Manna is referred to in Ps 78:24-25 as "the corn of heaven" and "angels' food" and again in Ps 105:40 as "the bread of heaven." In His letter to the church of Pergamos, Jesus referred to "the hidden manna" that He will give to overcomers to eat (Re 2:17).