The reason is doubtless because of the favorable auspices associated from time immemorial with the crescent moon.
One need hardly accept as plausible the explanation sometimes offered, namely, that the half-moon tavern symbol is a silent invitation to eat and drink to one’s full capacity; a hint, as it were, to follow the crescent moon’s example and “get full.”
XVIII. HORSE-SHOES ON CHURCH-DOORS
The origin of the horse-shoe as a charm has been ascribed to its resemblance to the metallic aureole or meniscus formerly placed over the heads of images of patron saints in churches, and which is also represented in ancient pictures of the Virgin.
This aureole, or more properly nimbus, was probably of pagan origin, for in early times circles of stars frequently ornamented the heads of statues of the gods, as emblematic of divinity. In speaking of certain ancient relics found in Ireland, Mr. W. G. Wood-Martin (“Pagan Ireland,” p. 492) says:—
Thin crescentic plates, with the extremities terminating in flat circular disks, are the ornaments most frequently discovered. In form they are identical with the half-moonshaped ornaments in use among the Greeks and Romans, and with the nimbi on carvings of the Byzantine school; and they differ but little from the ring which now is conventionally placed around the head of a saint. Thus this glory can be traced back to pagandom. The crescentic plate appears to have been primarily the badge of some distinguished person, a chief or king; then it became the emblem of one considered to be a very holy person, for in Ireland, in the early days of Christianity, the saints were derived principally from the aristocracy.
In the collection of the Royal Irish Academy is a golden tiara or diadem, said to have been found in County Clare. This relic, which measures about a foot in height and the same in breadth, is thought to have been a head-dress of some pagan or early Christian chieftain.
In the earlier years of the church these crescent symbols were avoided as savoring of heathenism; but without any thought of its significance, it became customary in the Middle Ages to place a circular brass plate upon the heads of statues as a protection from snow or rain. Hence arose the practice of similarly adorning images and paintings in churches.[217]
In later times these crescent-shaped pieces of metal were sometimes nailed up at the entrance of churches, and so came to be regarded as protective emblems.[218] The horse-shoe was an easily available substitute for the halo or glory, and so was often placed upon the doors of churches, especially in the southwest of England, as it was generally believed in olden times that evil spirits could enter even consecrated edifices. Aubrey, in his “Miscellanies,” mentions having seen under the porch of Staninfield Church, in Suffolk, an inscription with the device of a horse-shoe, intended to exclude witches, and he naïvely remarks that one would imagine holy water amply sufficient for the purpose.
On the south door of the parish church of Ashby-Foville, in Leicestershire, were formerly two ancient horse-shoes of great size, one of them measuring 16 by 11½ inches, or more than twice as large as an average modern shoe.