The word for today is…
buttress (noun) – 1. A structure, usually brick or stone, built against a wall for support or reinforcement.
2. Something resembling a buttress, as:
(a) The flared base of certain tree trunks.
(b) A horny growth on the heel of a horse’s hoof.
3. Something that serves to support, prop, or reinforce.
Source : The Free Dictionary
Etymology : Early 14th century, “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.” Figurative sense “any source of support” is from mid-15th century.