According to Robert Grave’s Celtic Tree calendar, June is the month of the Oak or ‘Duir’ (pronounced ‘DOO-r’) in old Irish gaelic.
‘Duir’ derives from the indo-european root ‘deru’ of which sprouts some very interesting shoots indeed – including, as you might expect ‘door’ but also the words ’tree’, ‘true’ and ’trust’.
From Wikipedia ..
‘Proto-IE *deru-, a cognate to English tree, is the word for “oak”, though the root has a wider array of meanings related to “to be firm, solid, steadfast” (whence e.g. English true).’
In Old English the words ‘true’ and ‘tree’ looked and sounded very alike – ‘true’ was ‘treowe’ and ‘tree’ was ‘treow’ – which in turn derived from the Germanic adjective ‘treuwaz’ and the noun ‘trewam’ .. both which again came from the Indo-European ’deru’ meaning ‘solid’ and ‘steadfast’, qualities that can as easily apply to truth as to trees 🙂
We’ve also been given the words ‘durable’, ‘duress’, ‘duration’ and ‘endurance’ from the same root – all again relating to solidity or firmness and/or steadfastness – ‘trust’ can also be thought of in these terms.
‘Druid’ also derives from ‘deru’ and can be translated as ‘oak knower’ or ‘truth seer’ – the Oak tree being the most sacred tree of the Druids who would make their wands from its wood.
This brings us back to ‘door’ as the Oak was thought to exist in the Celtic ‘Otherworld’ as well as this one so in essence a portal to another realm.
So it’s easy to see how the Oak is associated with the qualities of nobility, strength and protection 🙂

The Oak
Live thy Life,
Young and old,
Like yon oak,
Bright in spring,
Living gold;
Summer-rich
Then; and then
Autumn-changed
Soberer-hued
Gold again.
All his leaves
Fall’n at length,
Look, he stands,
Trunk and bough
Naked strength.
Alfred Lord Tennyson 1809-1892
Have a very Happy June! 🙂

Excellent post . Oak also derives from de proto-celtic word dari(k) or daru (proto-IE) like you said. And druid from proto-celtic druwid, always according with the profesor John T. Koch from University of Wales Centre for Advanced Welsh and Celtic Studies,
Aberystwyth. Any way, a valid translation of druid will be ‘oak knower’. As you told us. Thanks for sharing your amazing knowledge in this great blog
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Thanks Guss, that is so interesting! Thanks also for the compliments .. though I can assure you I am no expert on all of this, more of an enthusiast! 😉 Many thanks! 🙂
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