From Old English *bolster* (a long stuffed pillow or cushion), from Proto-Germanic *bulstraz*, related to *bolla* (bowl, round object). The noun referred to a cylindrical pillow used to prop someone up — a meaning that migrated naturally into the verb sense of "to prop up or support" by the 16th century.

*Bolster* is especially common in journalism, politics, and business writing — you'll often see headlines like "President moves to bolster economy" or "New study bolsters case for X." It carries a sense of reinforcing something that already exists but needs extra support, making it slightly different from *strengthen* (which can build from nothing).