The term ANCESTOR BRIDGE is composed of two words, the first being 'ANCESTOR' and the second being 'BRIDGE'. The crossword solution for the first word is INCA, which is an acronym for the INCA Empire, a pre-Columbian civilization that flourished in South America from the 12th to 16th centuries. The second word, 'BRIDGE', refers to the INCA's engineering feats, such as the suspension bridges they built across deep canyons. Therefore, the term ANCESTOR BRIDGE is a metaphor for the INCA's engineering accomplishments, which have been passed down through generations and continue to serve as a BRIDGE between the past and present.