the.com/heat shield

means A protective layer on a spacecraft, missile, or reentry vehicle that absorbs or deflects the intense heat generated when it plunges back through the atmosphere.

from A plain compound of two old workhorse words. 'Heat' descends from Old English 'hǣtu,' tied to 'hot,' both tracing back to a Proto-Germanic root for warmth. 'Shield' comes from Old English 'scield,' the warrior's board of wood and hide, from a Proto-Germanic root meaning 'to divide, separate, protect' — the same family that gives us 'shell.' The phrase itself is a creature of the 20th century, born in aviation and crystallized in the rocket-and-reentry vocabulary of the space age, when engineers literally needed a shield against heat to keep their ships from burning up.