fuel, firewood, kindling
薪 centers on material burned for heat or energy: firewood, kindling, or fuel in general.
薪 combines 艹 (grass/plant) with 新, which likely contributes the sound and the idea of freshly cut wood. The character originally referred to firewood gathered from plants.
Freshly cut grass and new wood piled together make fuel for a fire: 艹 on top of 新 suggests plant material that is new and ready to burn.
For シン, imagine a thin piece of kindling snapping as you add it to the fire: thin -> シン, and the thin wood fuels the flames.
piece(s) of firewood (esp. chopped or split from logs)
hatchet; axe
going through thick and thin to attain one's objective; enduring unspeakable hardships for the sake of vengeance
noh theater performed at night by a fire
kindling burned in shrines and temples
brushwood and firewood
having one's good intentions backfire dangerously; causing harm when trying to prevent it; trying to put out a fire while carrying kindling
wood-burning stove; wood stove
wood basket; firewood bucket; log holder
woodshed
firewood gathering
fuel and water; firewood and water
menial services (e.g. kitchen work); serving one's master unsparingly
Order for the Provision of Firewood and Water (1842)
wood and charcoal; fuel