The story
From Latin arbor (“tree”) + vitae (“of life”), literally “tree of life”, probably referring to the evergreen leaves. The anatomical sense from the branched, tree-like appearance of the tissue.
Etymology from Wiktionary, CC BY-SA 4.0.
arborvitae
Today it means: Any of several North American or Asian conifers, of the genera Thuja and Thujopsis or the species Platycladus orientalis, grown for timber or ornament. Full definition →