A downfall is the ruin of somebody who was riding high. His downfall, cause her downfall, the downfall of the regime.
The height matters: you cannot have a downfall without having been up, which is why the word attaches to leaders, champions and empires. It often names the cause too — pride was his downfall, drink was her downfall. Note that downfall also means heavy rain in older use, which is the literal sense the figurative one grew out of.
1noundownfallThe ruin of somebody who was riding high.
“The bribery scandal led to the minister's downfall only a year after his election.”
2nouncauseThe cause of that ruin.
“He was a talented man, but his love of gambling was his downfall.”
downfall is a ruin.
Down plus fall, written as two words from the thirteenth century and as one from the sixteenth. The literal sense of falling rain came first.
Middle English
doun
English
down
English, today
downfall
Built from
From down + fall. In this spelling, from 16th century; spelled as two words from 13th century. down comes from Middle English doun. From Middle English doun, doune (“down”), from Old English dūne (“down”), aphetic form of adūne (“down, downward”), from earlier ofdūne (“down”) literally “off the hill”, from of (“of, off of”) + dūn (“hill, mount, dune, down”). More at Etymology 2 below. For the development from directional phrases to prepositions, compare dene, dāle, whence dal. Compare also stq, del. Cognate with Scots doon (“down”).
Etymology from Wiktionary, CC BY-SA