Oakmen are male dwarf faeries who are the guardians of sacred oak groves. They are not very friendly towards people, but no one has ever been harmed by one. They are described as having huge heads being squat, dwarfish people with red caps. There land of origin is Germany and Scandinavia but scattered references have also been found in Northern England though very few folktales about them: there is no doubt that the oak was regarded as a sacred and potent tree.
Most people know the rhyming proverb 'Fairy folks are in old oaks'; 'The Gospel Oak' or 'The King's Oak' in every considerable forest had probably a traditional sacredness from unremembered times, and an oak coppice in which the young saplings had sprung from the stumps of felled trees was thought to be an uncanny place after sunset; but the references to 'oakmen' are scanty. An oak coppice was often considered an evil and dangerous place to travel through at night, especially if it was a blue-bell wood. Oakmen are created when an oak stump sends up shoots. One should never take food offered by them ; they may offer delicious food to passing mortals, but as soon as the fairy magic on them is reversed, you will see they are, in reality, bits of poisonous fungi. It is unwise to wander around felled oaks, as oakmen may be lingering around them, angry at the loss of their parent tree. They guard the wild animals of the forests and dwell near clumps of bluebells. If you damage bluebells in the woods the Oakmen will make sure you get lost! They can be found in oak groves, especially in the Black Forest of Germany.
The oak derives its Gaelic name, (Old Irish daur, Welsh derw) from the Sanskrit word duir, or "door" and since trees have their roots in the unseen world, they are believed to be doors to these realms. Druids, who worshipped within sacred oak groves, derived their name from this word, combined with the Indo-European root wid, 'to know', becoming the "Wise Ones of the Oakwood." Bluebells were known as fairy flowers. Beatrix Potter in THE FAIRY CARAVAN gives some description of the Oakmen, squat, dwarfish people with red toadstool caps and red noses who tempt intruders into their copse with disguised food made of fungi. The fairy wood in which they lurk is thrice-cut copse and is full of bluebells.
THE FAIRY CARAVAN is her only long book, and is scattered with folktales and beliefs. It is probable that her Oakmen are founded on genuine traditions. In Ruth Tongue's FORGOTTEN FOLK TALES OF THE ENGLISH COUNTIES there is a story from Cumberland, 'The Vixen and the Oakmen', in which the Oakmen figure as guardians of animals. This rests on a single tradition, a story brought back by a soldier from the Lake District in 1948, and may well have been subject to some sophistication, but these two together make it worth while to be alert for other examples.
The Oakmen may have actually been some type of humans who worshipped in tree settings like the Druids of the Celtic lands. Because of the need for secrecy they may have gathered only at night and in the guise of non-human beings, in much the same way witches once gathered in secret. But the fact that they have come into legends as Dwarves means we have to take their existence as faeries seriously, also.