The expression occurs in an old legend of Parsifal written in the Nordic language (akin to modern Icelandic). The legend originated in the 13th century and was probably based on Chrestien de Troyes. The Grail is here called “ganganda greida” — from gehend, moving or going about, and greida, meaning literally “things” and in this context indicating “provisions” or “nourishment”.
The legend is from a collection entitled Riddararsögur (Rittersagen = Legends of Knighthood), ed. by Dr. Eugen Kölbing, Strassburg, 1872.
For readers of German a most valuable book on the tremendous subject of the Grail is Dey Gral und seine Hüter (The Grail and its Guardians) by Dr. Rudolf Meyer (Verlag Urachhaus, Stuttgart, 1956). See pages 25 and 289.
The following passages from lectures 6 and 7 of the lecture-course given by Dr. Steiner at The Hague, March 1913 (The Effect of Occult Development upon the Self and the Sheaths of Man) help to convey the aspect of the Grail specifically conveyed in the expression “ganganda greida” — i.e. Wegzehrnug, nourishment or food while journeying along a path:
“The legend of the Holy Grail tells us of that miraculous food which is prepared from the finest activities of the sense-impressions and the finest activities of the mineral, extracts, whose purpose it is to nourish the noblest part of man all through the life he spends on earth; for it would be killed by anything else. This heavenly food is what is contained in the Holy Grail ...” (from lecture 6.)
“... We have heard what the Holy Grail contains. It contains that by which the physical instrument of man on earth must be nourished: the extract, the pure mineral extract which is obtained from all foods and which unites in the purest part of the human brain with the purest sense-impressions, impressions which come to us through our senses. Now, to whom is this food to be handed? It is really to be handed — as is revealed to us when from the exoteric story we enter into the esoteric presentation of it in the Mysteries — it is really to be handed to the human being who has obtained the understanding of what makes man mature enough gradually to raise himself consciously to what the Holy Grail is ...” (from lecture 7.)