From Middle English underberen (“to support”), from Old English underberan (“to support, endure”), equivalent to under- + beran (“to bear”). More at under-, bear.
underbear (third-person singular simple present underbears, present participle underbearing, simple past underbore or underbare, past participle underborne)
- To support, endure.
- (transitive) To line, guard or face a material, especially cloth.