sap

Etymology 1

From Middle English sap, from Old English sæp (“juice, sap”), from Proto-West Germanic *sap (“sap, juice”) (compare Dutch sap, German Saft, Icelandic safi), from Proto-Indo-European *sab-, *sap- (“to taste”) (compare Welsh syb-wydd (“fir”), Latin sapa (“must, new wine”), Russian со́пли (sópli, “snivel”), Old Armenian համ (ham, “taste”), Avestan 𐬬𐬌-𐬱𐬁𐬞𐬀 (vi-šāpa, “having poisonous juices”), Sanskrit सबर् (sabar, “juice, nectar”)). More at sage. The longstanding practice of sapping trees influenced the sense evolution of the military term as trench warfare receded from public conscience.

noun

1. (uncountable) The juice of plants of any kind, especially the ascending and descending juices or circulating fluid essential to nutrition.
2. (uncountable) The sapwood, or alburnum, of a tree.
3. Any juice.
4. (figurative) Vitality.
5. (slang, countable) A naive person; a simpleton.
   Look at the sap mowing our lawn while we pretend our own lawnmower is broken.
   She said I'm such a sap, I'm such a jerk / Can't I ever forget the way that we are / Spend all your time with your eyes on the ground / Looking for the stars 1997, “Don't Look Down”, in Curtains, performed by Tindersticks

verb

1. (transitive) To drain, suck or absorb from (tree, etc.).
2. (transitive, figurative) To exhaust the vitality of.
   While Tuchel will be delighted with the way his players responded, there will be concern at how much the energy-sapping 120 minutes has taken out of them. 12 April 2022, Neil Johnston, “Real Madrid 2-3 Chelsea”, in BBC Sport

Etymology 2

Probably from sapling.

noun

1. (countable, US, slang) A short wooden club; a leather-covered hand weapon; a blackjack.
   I risk my whole future, the hatred of the cops and Eddie Mars' gang. I dodge bullets and eat saps. 1944, William Faulkner, Leigh Brackett, Jules Furthman, The Big Sleep (screenplay)

verb

1. (transitive, slang) To strike with a sap (with a blackjack).
   [A]s he passes the mouth of a narrow alley two men step out quickly. One of them saps Marlowe expertly — they drag him out of sight. 1944, William Faulkner, Leigh Brackett, Jules Furthman, The Big Sleep (screenplay)
   And when he had me up there he would sap me again and I wouldn't remember anything that happened in between the two sappings. 1964, Raymond Chandler, Killer in the Rain

Etymology 3

From French saper (compare Spanish zapar and Italian zappare) from sape (“sort of scythe”), from Late Latin sappa (“sort of mattock”).

noun

1. (military) A narrow ditch or trench made from the foremost parallel toward the glacis or covert way of a besieged place by digging under cover of gabions, etc.

verb

1. (transitive) To subvert by digging or wearing away; to mine; to undermine; to destroy the foundation of.
2. (transitive, military) To pierce with saps.
3. (transitive) To make unstable or infirm; to unsettle; to weaken.
   Ring out the grief that saps the mind[…] 1850, Alfred Tennyson, Ring, Out, Wild Bells
4. (transitive) To gradually weaken.
   to sap one’s conscience
   he saps my energy
5. (intransitive) To proceed by mining, or by secretly undermining; to execute saps.