buttress (n.)

early 14c., "structure built against a wall to give it stability," from Old French (arc) botrez "flying buttress," apparently from bouter, boter "to thrust against," a word of Frankish origin (compare Old Norse bauta "to strike, beat"), from Proto-Germanic *butan, from PIE root *bhau- "to strike." The figurative sense "any source of support" is from mid-15c.

"support by a buttress; prop or prop up," late 14c., literal and figurative, from buttress (n.). Related: Buttressed; buttressing.