A Herma (Ancient Greek: ἑρμῆς, pl ἑρμαῖ “hermai”), is a sculpture with a head above a plain, usually squared lower section, on which male genitals may also be carved at the appropriate height, originating in Ancient Greece. In the earliest times Greek divinities were worshiped in the form of a heap of stones or a shapeless column of stone or wood. There were in many parts of Greece piles of stones by the sides of roads, especially at their crossings, and on the boundaries of lands. The religious respect paid to such heaps of stones, especially at the meeting of roads, is shown by the custom of each passer-by throwing a stone on to the heap or anointing it with oil. Later there was the addition of a head and phallus to the column, which became quadrangular (the number 4 was sacred to Hermes). The phallus formed an essential part of the symbol, probably because the divinity represented by it was in the earliest times, before the worship of Dionysus was imported from the East, the personification of the reproductive powers of nature.
In ancient Greece the statues had an apotropaic function and were placed at crossings, country borders and boundaries as protection, in front of temples, near to tombs, in the gymnasia, palaestrae, libraries, porticoes, and public places, at the corners of streets, on high roads as sign-posts, with distances inscribed upon them. Before his role as protector of merchants and travelers, Hermes was a phallic god, associated with fertility, luck, roads and borders. His name comes from the word herma referring to a square or rectangular pillar of stone, terracotta, or bronze; a bust of Hermes’ head, usually with a beard, sat on the top of the pillar, and male genitals adorned the base. In Athens, the hermai were most numerous and most venerated, they were placed outside houses as apotropes for good luck. They would be rubbed or anointed with olive oil and adorned with garlands or wreaths. This superstition persists, for example the Porcellino bronze boar of Florence (and numerous others like it around the world), where the nose is shiny from being continually touched for good luck or fertility.