*deru-, *dreu-

The core idea of this root was

firm, hard, strong

It has evolved into quite an impressive language tree where the two main branches in English are about lasting over time (during, duration, durable, endurance) and being steadfast, honest (trust, truth, true)

Here’s a little (incomplete) overview:

• tree
• dendro- (Greek stem for tree)
• Druid (literally “tree-wit, tree, knower”)
• dryad (“wood nymph”)
• duration, during, endurance, durable
• trust
• truth, true
• duress (originally:” hardness”, then “toughness”)