late 14c., "statement, belief, or practice handed down from generation to generation," especially "belief or practice based on Mosaic law," from Old French tradicion "transmission, presentation, handing over" (late 13c.) and directly from Latin traditionem (nominative traditio) "delivery, surrender, a handing down, a giving up," noun of action from past-participle stem of tradere "deliver, hand over," from trans- "over" (see trans-) + dare "to give" (from PIE root *do- "to give"). The word is a doublet of treason (q.v.). Meaning "a long-established custom" is from 1590s. The notion is of customs, ways, beliefs, doctrines, etc. "handed down" from one generation to the next.
Tradition is not solely, or even primarily, the maintenance of certain dogmatic beliefs; these beliefs have come to take their living form in the course of the formation of a tradition. What I mean by tradition involves all those habitual actions, habits and customs, from the most significant religious rite to our conventional way of greeting a stranger, which represent the blood kinship of 'the same people living in the same place'. ... We become conscious of these items, or conscious of their importance, usually only after they have begun to fall into desuetude, as we are aware of the leaves of a tree when the autumn wind begins to blow them off--when they have separately ceased to be vital. Energy may be wasted at that point in a frantic endeavour to collect the leaves as they fall and gum them onto the branches: but the sound tree will put forth new leaves, and the dry tree should be put to the axe. [T.S. Eliot, "After Strange Gods"]