The Gaelic and Sanskrit word duir (pronouced doo-ear) refering to the oak tree also conveys solidity and protection, the English word door comes from the same root.
...from The Celtic Tree Oracle by Liz and Colin Murray

Oaks eventually become very big trees, and are probably best recognised close-up by the leaves, acorns or acorn cups that they have dropped. The leaves are typically longer than they are wide, and wider nearer the tip than near the (very short) stem where they join the tree. Generally leaf edges are shaped 'the oposite way from Holly' that is there are pointy angles going in toward the leaf and round bulges coming out away from the leaf, however a few species are holly-leaf shaped. If the acorn needs description think of a streched egg stuck into an eggcup which hangs upsidedown. The cup is generally covered in little round bobbles or else 'hairs'. The oak has male catkins near the end of its shoots and small female flowers slighly further in. Catkins come out in May / June, and their pollen causes hay-fever in some people.

You could try growing an oak from an acorn, but unless you have a very big garden you and your neighbours might soon start to miss the direct sunlight that you once enjoyed. The shape of oak trees is extreemely variable. sometimes producing tall ragged crowns up to 135 feet (45 metres) high, more usually a massive twisting dome less than 60 feet (20 m) high. This is when the leading shoot is lost due to human copicing, animal attack or disease.
...from Trees by Alastaire Fitter and David More

There were no references to medicinal uses of oak derivatives in the couple of source books that I had available other than that acorns have been eaten in times of famine, and roasted as an ingredient of erstaz coffee during the twentieth century wartime blockades.

The oak's shamanistic stations are mid-April, Summer Solstice, Lughnasadh, and September/October for acorns.

Duir, Dur, Daroch, Der, Derwen, are linked to the root of the word draoidh in Gaelic meaning wise man magician or druid. Initiation by the Faerie beings or wildfolk lies beyond the oaken door in Taliesin's poems. The tree is associated with Taran or Taranis a Celtic god of thunder, and movement of oak branches was sometimes used as an oracle of the sky gods' wishes. Oak and holly 'Knights' are said to fight over the lady Keirddylad every Beltaine. Oak rules from Beltain to Samhain, and Holly the rest of the year.

Druids and many Celtic Saints preached in oak groves, among the latter are St. Kentigern, St. Brigit and St. Columba. Some traditions say that Oak should only be felled with a double axe. If the bark of oak is to be separated from the trunk it should be felled in April when the moon is decreasing and the wind not in the East. Oak apple day was originally celebrated ... on May 29th then later transferred to 10th June as part of Whitsun celebrations. In east anglia children who did not wear oak leaves or oak apples on May 29th would be pinched or stung with nettles by their companions. A fresh flush of leaves on long thin stalks is often seen in Scotland around Lughnasadh and is called Lammas growth or Lammas shoots.
...from Keltic Folk and Faerie Tales by Kaledon Naddair

The Oak is the Summer King of the wild wood. He stands mightily solid in both root and branch. He is often struck by lightning whose heat boils the sap and bursts the stem apart leaving the trunk gnarled and withered. Still the oak often manages to survive for centuries with a slow but sure growth.

The oak's place in the Celtic lunar calendar is the seventh of thirteen months making the transition from spring to summer, coming after Huath (Hawthorne) and before Tinne (Holly).

Oaks have been used to mark boundaries between one area and the next, and as open air preaching places for Ovates Bards and Druids.
...from The Celtic Tree Oracle by Liz and Colin Murray

The oaks of Celtic and Norse legend (today classified as European Oak) refer to just two of the 400 or so separate species in the genus Quercus. Both Q. robur and Q.petraea which tends to live in warmer lighter soils may be called English, Polish, Slavonian or White oak by craftsmen. The oak has held a special fascination since the earliest times the tree was sacred to the Celts and Greeks. This King of British woodland trees, believed to live for over 1000 years, was the foremost construction material in Europe, and the most important furniture timber from the middle ages until the 17th century when it was overtaken by walnut.

Some 500 species of insects and other invertebrates depend to a greater or lesser extent on oak foliage, bark or timber for their existence. They in turn are an important food source for birds. In Saxon times poor people are recorded as eating acorns in periods of famine and towards the end of the seventh century laws were passed on the feeding of domestic pigs in the 'forests' (hunting estates) on acorns and beech mast. These rites of 'pannage' are still observed in the 'New Forest' of Hampshire. Oaks are also important for their ability to help drain clay soils drawing up around 20 gallons (90 litres) of water per day.

Much of southern England still had a large amount of oak woodland until 1945. Between 1945 and 1985 over half the remaining hardwood was clear felled or severely degraded - an amount equivalent to that destroyed in the previous 400 years. Since then the British Woodland Trust has begun to purchase some softwood plantations from the Forestry Commission and replant them in hardwood as they mature. In recent years the health of oak woodland all over Europe has declined with the most serious losses in Germany the Czech and Slovak Repubilcs and Poland.

Not only very strong but durable, the natural formation of oak branches allowed timber to be cut from the tree in the best curved shapes for cruck framed roofs or for ship frames. Oak has a long history of use inside churches and cathedrals and for barrel making. It has also been used in tanneries to process leather and as fuel in early iron smelting particularly in the Weald of Kent / Sussex The cork-oak Q. suber provides a honeycom of airtight cells bound with a resin and filled with an air like gas. It is used as a bottle stopper, and a sound or vibration insulator. This outher layer of bark is stripped from the growing layer with a special axe in June, July or August, and can be taken from a tree every nine years without harming it.
...from Plants for People by Anna Lewington