in reference to a type of northern Indian and Pakistani cooking using a charcoal-fired clay oven, 1958, from adjectival form of Urdu or Punjabi tandur "cooking stove," a regional word of uncertain origin. As a noun by 1969.
1590, one of the three fundamental functions of trigonometry, from tangent (adj.). From 1650s as "a tangent line." Figurative use of on a tangent is from 1771.